A070555 Sum of positive integers k, where k <= n and gcd(k,2n+1) = gcd(k+1,2n+1).

1, 1, 6, 15, 12, 45, 66, 21, 120, 153, 50, 231, 180, 117, 378, 435, 144, 255, 630, 209, 780, 861, 198, 1035, 840, 375, 1326, 729, 476, 1653, 1770, 465, 1056, 2145, 714, 2415, 2556, 555, 1710, 3003, 1080, 3321, 1890, 1161, 3828, 2475, 1334, 2397, 4560, 1323

Offset

1,3

Comments

Note that whenever gcd(k,2n+1) = gcd(k+1,2n+1), this common value must be 1. - David Wasserman, May 13 2003

Links

Table of n, a(n) for n=1..50.

Prog

(MATLAB) function m = A070555(n) m = 0; for k = 1:(2*n + 1) if gcd(k, 2*n + 1) == gcd(k + 1, 2*n + 1) m = m + k; end end

Crossrefs

Bisection of A069828.

Sequence in context: A161397 A145257 A245200 * A265388 A334352 A128512

Adjacent sequences: A070552 A070553 A070554 * A070556 A070557 A070558

Keyword

nonn

Author

Vladeta Jovovic, Apr 29 2002

Extensions

More terms from David Wasserman, May 13 2003

Status

approved