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 A160973 #11 Dec 15 2018 22:30:02 %S A160973 0,0,0,0,0,0,1,0,0,1,0,1,1,0,0,1,2,0,1,0,0,3,0,1,1,0,2,1,0,0,3,2,0,1, %T A160973 0,0,3,2,0,2,0,2,1,0,2,1,2,0,3,0,0,5,0,0,1,0,2,3,2,1,1,2,0,1,0,2,5,0, %U A160973 0,1,2,2,3,0,0,3,2,0,1,2,0,5,0,1,3,0,4,1,0,0,1 %N A160973 a(n) is the number of positive integers of the form (n-3k)/(2k+1), 1 <= k <= (n-1)/5. %C A160973 If n is different from 3, then a(n)=0 iff n is in A067076, i.e., 2n+3 is prime. %t A160973 a[n_] := Length[Select[Range[Floor[(n-1)/5]], IntegerQ[(n-3#)/(2#+1)] &]]; Array[a, 100, 0] (* _Amiram Eldar_, Dec 15 2018 *) %o A160973 (PARI) a(n) = sum(k=1, (n-1)/5, frac((n-3*k)/(2*k+1)) == 0); \\ _Michel Marcus_, Dec 15 2018 %Y A160973 Cf. A067076, A034953, A054269, A082749, A006254, A161116. %K A160973 nonn %O A160973 0,17 %A A160973 _Vladimir Shevelev_, Jun 01 2009, Jun 07 2009 %E A160973 Edited by _N. J. A. Sloane_, Jun 07 2009 %E A160973 a(44) corrected and more terms from _Michel Marcus_, Dec 15 2018