login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A211769 Greater of twin primes p, p+2 with unique values of sigma(p) and sigma(p+2); sigma(n) = A000203(n) = sum of divisors of n. 4
5, 7, 199, 283, 349, 463, 643, 823, 859, 1291, 1699, 1723, 1789, 1879, 2083, 2143, 2383, 2551, 2803, 3259, 3541, 3559, 3931, 4021, 4243, 4639, 4723, 5443, 5479, 5503, 5659, 6451, 6691, 6703, 6763, 6829, 6949, 7459, 7591, 7879, 8011, 8389, 8539, 8599, 8629 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Subsequence of A211656, A211660, and A211678.
LINKS
EXAMPLE
Prime 199 is in sequence because 197 and 199 are twin primes, sigma(197) = 198, sigma(199) = 200 and there are no other numbers m, n with sigma(m) = 198 or sigma(n) = 200.
MATHEMATICA
d = DivisorSigma[1, Range[10000]]; t = Transpose[Select[Tally[Sort[d]], #[[2]] == 1 && #[[1]] <= Length[d] &]][[1]]; t2 = Sort[Flatten[Table[Position[d, i], {i, t}]]]; t3 = Select[t2, PrimeQ]; tp = {}; Do[If[t3[[i + 1]] - t3[[i]] == 2, AppendTo[tp, t3[[i + 1]]]], {i, Length[t3] - 1}]; tp (* T. D. Noe, Apr 26 2012 *)
CROSSREFS
Cf. A211678 (twin primes p, p+2 with unique values of sigma(p) and sigma(p+2)), A211767 (lesser of twin primes p, p+2 with unique values of sigma(p) and sigma(p+2)).
Sequence in context: A123536 A057177 A297535 * A265031 A229030 A229033
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, Apr 20 2012
EXTENSIONS
A-number corrected by Jaroslav Krizek, Mar 17 2013
STATUS
approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified April 20 17:12 EDT 2024. Contains 371845 sequences. (Running on oeis4.)