A081515 Sum of terms in n-th row of A081517.

1, 3, 7, 11, 17, 23, 29, 37, 47, 59, 67, 79, 97, 107, 127, 137, 157, 173, 191, 211, 233, 257, 277, 307, 331, 353, 379, 409, 439, 467, 499, 541, 563, 599, 631, 673, 709, 743, 787, 821, 863, 907, 947, 991, 1039, 1087, 1129, 1181, 1229, 1277, 1327, 1381, 1433, 1487

Offset: 1

Author

Amarnath Murthy, Mar 27 2003

Keywords

• nonn
• changed

Comments

a(n) is > the n-th triangular number. Conjecture: There are no composite members.

How is this related to A065383 and A077128? - R. J. Mathar, Aug 27 2025

Crossrefs

Cf. A081516, A081517.

Programs

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

Extensions

a(7)-a(9) from R. J. Mathar, Mar 23 2007

More terms from Jinyuan Wang, May 23 2020