This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A227757 #15 Apr 18 2025 08:54:41 %S A227757 23,29,41,53,101,113,137,173,257,281,317,353,401,617,641,653,677,761, %T A227757 821,941,977,1181,1193,1359,1361,1373,1433,1613,1697,1877,1901,2081, %U A227757 2153,2237,2273,2297,2333,2381,2633,2657,2693,2741,2777,2801,3137,3413,3461,3557 %N A227757 Numbers k such that antisigma(k) = antisigma(k+1) + 12; where antisigma(k) = A024816(k). %C A227757 Supersequence of A227756 (primes p such that sigma(p+1) = 2*p+14). %C A227757 The composites in this sequence are rare: 1359, 453967, ... (no more up to 10^6). %H A227757 Jaroslav Krizek, <a href="/A227757/b227757.txt">Table of n, a(n) for n = 1..500</a> %e A227757 1359 is in sequence because antisigma(1359) = 922144 = antisigma(1360) + 12 = 922132 + 12. %t A227757 Select[Range[3600],DivisorSigma[1,#+1]-DivisorSigma[1,#]==#+13 &] (* _Stefano Spezia_, Apr 18 2025 *) %o A227757 (PARI) is(n)=sigma(n+1)-sigma(n)==n+13 \\ _Charles R Greathouse IV_, Nov 25 2014 %Y A227757 Cf. A024816, A227756. %K A227757 nonn %O A227757 1,1 %A A227757 _Jaroslav Krizek_, Jul 26 2013