A115012 -id:A115012 - cp's OEIS frontend

A115014 a(n) = Sum_{i=1..n, gcd(6,i)=1} i.

1, 1, 1, 1, 6, 6, 13, 13, 13, 13, 24, 24, 37, 37, 37, 37, 54, 54, 73, 73, 73, 73, 96, 96, 121, 121, 121, 121, 150, 150, 181, 181, 181, 181, 216, 216, 253, 253, 253, 253, 294, 294, 337, 337, 337, 337, 384, 384, 433, 433, 433, 433, 486, 486, 541, 541, 541, 541, 600, 600, 661

Offset: 1

N. J. A. Sloane, Feb 24 2006

Cf. A115012.

Table[Sum[k*KroneckerDelta[GCD[6, k], 1], {k, n}], {n, 80}] (* Wesley Ivan Hurt, Jan 20 2024 *)

A115015 Sum_{i=1..n} (gcd(7,i)=1) i.

Original entry on oeis.org

1, 3, 6, 10, 15, 21, 21, 29, 38, 48, 59, 71, 84, 84, 99, 115, 132, 150, 169, 189, 189, 211, 234, 258, 283, 309, 336, 336, 365, 395, 426, 458, 491, 525, 525, 561, 598, 636, 675, 715, 756, 756, 799, 843, 888, 934, 981, 1029, 1029, 1079, 1130, 1182, 1235, 1289, 1344, 1344

Offset: 1

N. J. A. Sloane, Feb 24 2006

nonn

Cf. A115012.

a(n)=binomial(n+1,2)-7*binomial(n\7+1,2) /* Michael Somos, Jul 12 2006 */

a(n)=sum(i=1,n, i*(1==gcd(7,i))) /* Michael Somos, Jul 12 2006 */

a(-1-n) = a(n). - Michael Somos, Jul 12 2006

cp's OEIS Frontend

A115014 a(n) = Sum_{i=1..n, gcd(6,i)=1} i.

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