A394374 a(n) = Sum_{i=1..n} (2*i-1)^(2*i).

1, 82, 15707, 5780508, 3492564909, 3141920941630, 3940518306640919, 6572348874019531544, 14069656800941744522553, 37604043114346899937878154, 122731931429219979848941490995, 480373495927931196770014698434036, 2220926422746241012044033350880074661

Offset

1,2

Links

Table of n, a(n) for n=1..13.

Formula

a(n) = a(n-1) + (2*n-1)^(2*n) for n > 1, with a(1) = 1.

a(n) ~ exp(-1) * 2^(2*n) * n^(2*n). - Vaclav Kotesovec, Jun 01 2026

Example

a(3) = 1^2 + 3^4 + 5^6 = 1 + 81 + 15625 = 15707.

Prog

(PARI) vector(13, n, sum(i=1, n, (2*i-1)^(2*i))) \\ Rayhan Ahmed, Jun 01 2026

Crossrefs

Partial sums of A222621.

Cf. A001923, A062815, A222621, A338167, A338168.

Sequence in context: A280361 A280671 A241129 * A289330 A282157 A176024

Adjacent sequences: A394371 A394372 A394373 * A394375 A394376 A394377

Keyword

nonn,easy

Author

Rayhan Ahmed, Jun 01 2026

Status

approved