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Sequence of the Day (archive)

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The Sequence of the Day (archive) page is in reverse chronological order of year and month. For current month, see Future (next 2 months) OEIS Wiki contributors to SoD.

November 2010

OEIS Wiki contributors for November 2010 Sequence of the Day
Date[1] OEIS Wiki contributor Sequence of the Day Comment
1  Alonso del Arte A118372 -perfect numbers. Cf. Granville numbers
2  Alonso del Arte A090232 First year in office of -th President of the United States of America. U. S. Election Day
3  M. F. Hasler A098516 Minimum wind speed in mph for a category hurricane in the Saffir-Simpson hurricane scale. Max has a draft on one of his user subpages.
4  Alonso del Arte A001783 The "phi-torial" of . Cf. Euler's totient function or phi(n);

means i does not divide n (not what we want, would be wanted for "nondivisorial,")

(what we want for "phitorial" or "coprimorial.")

5  Alonso del Arte A001567 Fermat pseudoprimes to base 2. (Sarrus numbers or Poulet Numbers) Cf. Fermat pseudoprimes
6  Alonso del Arte A083216 Fibonacci-like primefree sequence.  
7  Alonso del Arte A018226 Magic numbers.  
8  Alonso del Arte A002372 Number of decompositions of 2 into ordered sums of two odd primes. Cf. Goldbach conjecture
9  Alonso del Arte A001491 Opus numbers of Beethoven's 9 Symphonies.  
10  Alonso del Arte A059999 {2, 3, 5, 7, 11, 42, ...} Wiggles through the first 5 primes, then gives up...

Since a polynomial of degree k can be fitted to wiggle through k+1 points, a polynomial of degree 5 could be fitted to wiggle through primes 2, 3, 5, 7, 11, 13.

11  Alonso del Arte A053664 Smallest number such that for Cf. Chinese remainder theorem | Veterans' Day.
12  Daniel Forgues A024702 , where = prime Subsequence of generalized pentagonal numbers (Cf. A001318.)

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13  Alonso del Arte A175607 Largest number such that the greatest prime factor of is . Proof that there is such a largest for each prime ?
14  Alonso del Arte A038770 Numbers divisible by at least one of their base 10 digits.  
15  Alonso del Arte A001468 Another version of the infinite Fibonacci word.  
16  Alonso del Arte A038699 Smallest prime of form or 0 if no such prime exists.  
17  Alonso del Arte A090206 Composite Fibonacci numbers (or intersection of A000045 and A002808.)  
18  Alonso del Arte A051254 Mills primes, obtained by computing , where is Mills' constant.  
19  Alonso del Arte A034872 Central column of Lozanić's triangle.  
20  Alonso del Arte A017354

(A098403 Area of Mandelbrot set.)

Related to heptagonal numbers (A000566.)

Birthday of Benoit Mandelbrot. (If no one else does the write-up by 22:00, Al will choose a different sequence.)

21  Alonso del Arte A081119 Number of integral solutions to Mordell's equation .  
22  Alonso del Arte A038772 Numbers not divisible by any of their base 10 digits. Primes in this sequence obviously can't have any of their digits be 1.
23  Alonso del Arte A115020 Count backwards from 100 in steps of 7. Sometimes used to gauge the concentration ability of a patient with Alzheimer's disease.
24  Alonso del Arte A167452 Smallest sequence which lists the position of digits "2" in the sequence.  
25  Alonso del Arte A103225 Gaussian integer equivalent to the totient function Thanksgiving.
26  Alonso del Arte A097545 / A097546 Farey fraction approximations to π  
27  Daniel Forgues Axxxxxx Odd spoof perfect numbers (only one term known: Descartes' 198585576189!) Cf. A058007 Freestyle perfect numbers: perfect numbers and spoof perfect numbers.
28  Alonso del Arte A104272 Ramanujan primes.  
29  Alonso del Arte A003052 Base 10 self numbers.  
30  Alonso del Arte A028442 Zeros of the Mertens function.  


  1. By the date is a link to the last edit of SoD for the given date.


October 2010

OEIS Wiki contributors for October 2010 Sequence of the Day
Date[1] OEIS Wiki contributor Sequence of the Day Comment
1 N/A N/A  
2 N/A N/A  
3 N/A N/A  
4 N/A N/A  
5 N/A N/A  
6 N/A N/A  
7 N/A N/A  
8 N/A N/A  
9 N/A N/A  
10  Alonso del Arte A020988 (2/3)*(4^n-1). Birthday of Sequence of the Day and birthday of Neil Sloane.
11  Alonso del Arte A005820 3-perfect (triply perfect, tri-perfect, triperfect or sous-double) numbers: sum of divisors of n is 3n.  
12  Daniel Forgues A092291 Let p = n-th irregular prime, A000928(n). Then a(n) = smallest value of m such that numerator(Bernoulli(2*m)/(2*m)) / numerator(Bernoulli(2*m)/(2*m*(2*m-1))) equals p.  
13  Jaume Oliver Lafont A006720 Somos-4 sequence: a(0)=a(1)=a(2)=a(3)=1; for n >= 4, a(n)=(a(n-1)a(n-3)+a(n-2)^2)/a(n-4).  
14  Maximilian Hasler A057652 Numbers n such that n-2^k is a lucky number for all k such that 1 < 2^k < n.  
15  Alonso del Arte A014437 Odd Fibonacci numbers.  
16  Alonso del Arte A118130 Composite lucky numbers whose divisors are also lucky numbers. C++ program that generates n lucky numbers in order
17  Alonso del Arte A027884 Figaro's opening aria in 'Le Nozze di Figaro' by Mozart.  
18  David W. Wilson A020639 lpf(n): least prime dividing n (a(1) = 1).  
19  Daniel Forgues A014580 Binary irreducible polynomials (primes in ring GF(2)[ X ]), evaluated at X=2. Carryless arithmetic base 2
20  Charles R Greathouse IV A177854 Smallest prime of rank n.  
21  T. D. Noe A000029 Number of necklaces with n beads of 2 colors, allowing turning over. Birthday of Martin Gardner
22  Alonso del Arte A005349 Harshad numbers.  
23  David W. Wilson A036236 Least positive number k such that the remainder when 2^k is divided by k is n.  
24  Alonso del Arte A070308 Numbers such that the sum of each base 10 digit squared adds up to the sum of the proper divisors.  
25  Alonso del Arte A036787 Numbers requiring as many digits in base 10 as in Roman numerals.  
26  Alonso del Arte A080035 "Orderly" Friedman numbers (or "good" Friedman numbers): Friedman numbers (A036057) where the construction digits are used in the proper order. Cf. Category:Nice Friedman numbers
27  Alonso del Arte A035327 Write n in binary, interchange 0's and 1's.  
28  Alonso del Arte A006567 Base 10 emirps.  
29  Alonso del Arte A069151 Base 10 Smarandache-Wellin primes.  
30  Alonso del Arte A030101 Convert n to binary, reverse the bits, and convert back to decimal.  
31  Alonso del Arte A008595 Multiples of 13. Halloween.


  1. By the date is a link to the last edit of SoD for the given date.