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 A081515 #12 Aug 27 2025 08:29:00
%S A081515 1,3,7,11,17,23,29,37,47,59,67,79,97,107,127,137,157,173,191,211,233,
%T A081515 257,277,307,331,353,379,409,439,467,499,541,563,599,631,673,709,743,
%U A081515 787,821,863,907,947,991,1039,1087,1129,1181,1229,1277,1327,1381,1433,1487
%N A081515 Sum of terms in n-th row of A081517.
%C A081515 a(n) is > the n-th triangular number. Conjecture: There are no composite members.
%C A081515 How is this related to A065383 and A077128? - _R. J. Mathar_, Aug 27 2025
%o A081515 (PARI) a(n) = {my(m=n*(n-1)/2, v); for(k=m+n, oo, v=List([1]); for(i=2, k-m, if(gcd(k, i)==1, listput(v, i))); if(#v>=n, forsubset([#v, n], w, if(sum(i=1, n, v[w[i]])==k, return(k))))); } \\ _Jinyuan Wang_, May 23 2020
%Y A081515 Cf. A081516, A081517.
%K A081515 nonn,changed
%O A081515 1,2
%A A081515 _Amarnath Murthy_, Mar 27 2003
%E A081515 a(7)-a(9) from _R. J. Mathar_, Mar 23 2007
%E A081515 More terms from _Jinyuan Wang_, May 23 2020