A077128 -id:A077128 - cp's OEIS frontend

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

Amarnath Murthy, Mar 27 2003

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

Cf. A081516, A081517.

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

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

More terms from Jinyuan Wang, May 23 2020

A077130 Smallest number which is relatively prime to all the numbers between n^2 and (n+1)^2, inclusive.

Original entry on oeis.org

5, 11, 17, 13, 19, 17, 23, 29, 37, 31, 29, 43, 41, 47, 37, 59, 41, 53, 59, 79, 61, 53, 73, 71, 89, 61, 79, 71, 83, 89, 79, 73, 83, 103, 101, 107, 97, 103, 89, 113, 127, 103, 97, 107, 101, 131, 137, 127, 109, 131, 113, 149, 127, 179, 131, 149, 179, 167, 139, 149

Offset: 1

Amarnath Murthy, Oct 29 2002

nonn

Naturally every member is a prime.

			a(5) = 19 is the smallest number coprime to all the numbers from 25 to 36.

Cf. A077128, A077129.

for(k=1,100,a=0:forprime(p=2,10001,f=0:for(l=k*k,(k+1)^2,if(gcd(p,l)>1,f=1:break)): if(!f,a=p:break)): if(a,print1(a","),print1("-,")))

Corrected and extended by Ralf Stephan, Mar 19 2003

cp's OEIS Frontend

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

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