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A246371 Numbers n such that, if 2n-1 = Product_{k >= 1} (p_k)^(c_k) then n > Product_{k >= 1} (p_{k-1})^(c_k), where p_k indicates the k-th prime, A000040(k). 14
5, 8, 11, 13, 14, 17, 18, 23, 28, 32, 38, 39, 41, 43, 50, 53, 58, 59, 61, 63, 68, 73, 74, 77, 83, 86, 88, 94, 95, 98, 104, 113, 116, 122, 123, 128, 131, 137, 138, 140, 143, 149, 158, 163, 167, 172, 173, 176, 179, 182, 185, 188, 193, 194, 200, 203, 212, 213, 215, 218, 221, 228, 230, 233, 238, 239, 242, 248, 254, 257 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Numbers n such that A064216(n) < n.

Numbers n such that A064989(2n-1) < n.

From Matthijs Coster, Dec 22 2014: (Start)

Also area of (over 45 degree) rotated rectangles with sides > 1. The area of such rectangles is 2ab - a - b + 1 = 1/2((2a-1)(2b-1)+1).

Example: Here a = 3 and b = 5. The area = 23.

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Note: I think the above comment applies to A053726, not this sequence, but I could be wrong (pending Matthijs Coster's further comments). - Antti Karttunen, Apr 17 2015

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..10000

Matthijs Coster, Oplossing Zomerprijsvraag, Pythagoras 54/2 (2014) 4-7.

PROG

(PARI)

default(primelimit, 2^30);

A064989(n) = {my(f); f = factor(n); if((n>1 && f[1, 1]==2), f[1, 2] = 0); for (i=1, #f~, f[i, 1] = precprime(f[i, 1]-1)); factorback(f)};

A064216(n) = A064989((2*n)-1);

isA246371(n) = (A064216(n) < n);

n = 0; i = 0; while(i < 10000, n++; if(isA246371(n), i++; write("b246371.txt", i, " ", n)));

(Scheme, with Antti Karttunen's IntSeq-library)

(define A246371 (MATCHING-POS 1 1 (lambda (n) (< (A064216 n) n))))

CROSSREFS

Complement: A246372.

Setwise difference of A246361 and A048674.

Subsequence of A104275 and A053726 (20 is the first term > 1 which is not in this sequence).

Subsequence: A246374 (the primes present in this sequence).

Cf. A000040, A064216, A064989, A246351.

Sequence in context: A294675 A104275 A053726 * A274939 A173977 A161537

Adjacent sequences:  A246368 A246369 A246370 * A246372 A246373 A246374

KEYWORD

nonn

AUTHOR

Antti Karttunen, Aug 24 2014

STATUS

approved

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Last modified November 19 03:27 EST 2019. Contains 329310 sequences. (Running on oeis4.)