The On-Line Encyclopedia of Integer Sequences (OEIS)

A094260 revision #8

A094260

Sum of next n numbers/n if n divides the sum else n times the sum of next n numbers.

1, 10, 5, 136, 13, 666, 25, 2080, 41, 5050, 61, 10440, 85, 19306, 113, 32896, 145, 52650, 181, 80200, 221, 117370, 265, 166176, 313, 228826, 365, 307720, 421, 405450, 481, 524800, 545, 668746, 613, 840456, 685, 1043290, 761, 1280800, 841, 1556730, 925, 1875016, 1013, 2239786

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

COMMENTS

Quasipolynomial of order 2 and degree 5. - Charles R Greathouse IV, Oct 14 2013

LINKS

Table of n, a(n) for n=1..46.

Index entries for linear recurrences with constant coefficients, signature (0,5,0,-10,0,10,0,-5,0,1).

FORMULA

For even n, a(n) = A000217(n^2) = n^2*(n^2+1)/2; for odd n, a(n) = (n^2 + 1)/2.

EXAMPLE

The sequence is: 1/1, (2+3)*2, (4+5+6)/3, (7+8+9+10)*4, ...