A382156 Partial sums of A382155.

1, 3, 9, 15, 31, 41, 65, 79, 111, 129, 169, 191, 239, 265, 321, 351, 415, 449, 521, 559, 639, 681, 769, 815, 911, 961, 1065, 1119, 1231, 1289, 1409, 1471, 1599, 1665, 1801, 1871, 2015, 2089, 2241, 2319, 2479, 2561, 2729, 2815, 2991, 3081, 3265, 3359, 3551, 3649, 3849, 3951, 4159, 4265, 4481, 4591, 4815, 4929, 5161, 5279, 5519

Offset

0,2

Links

Paolo Xausa, Table of n, a(n) for n = 0..10000

Index entries for linear recurrences with constant coefficients, signature (1,2,-2,-1,1).

Formula

a(n) ~ 3*n^2/2. - Charles R Greathouse IV, May 28 2026

Mathematica

LinearRecurrence[{1, 2, -2, -1, 1}, {1, 3, 9, 15, 31, 41, 65}, 100] (* Paolo Xausa, Mar 24 2025 *)

Prog

(PARI) a(n)=if(n>1, (3*n^2+(4-n%2*2)*n+[-2, -3][n%2+1])/2, 2*n+1) \\ Charles R Greathouse IV, May 28 2026

Crossrefs

Cf. A319384, A382154, A382155.

Sequence in context: A099409 A002127 A357764 * A061810 A048701 A031159

Adjacent sequences: A382153 A382154 A382155 * A382157 A382158 A382159

Keyword

nonn,easy,changed

Author

N. J. A. Sloane, Mar 23 2025

Status

approved