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A370191
a(n) is the numerator of the real part of 1/(1+i/2)^n, where i is the imaginary unit.
2
1, 4, 12, 16, -112, -1216, -7488, -35584, -134912, -367616, -242688, 5410816, 48140288, 276905984, 1252442112, 4481417216, 10802495488, -3208380416, -241716953088, -1869568016384, -10122205069312, -43586280226816, -146246140428288, -298243518889984, 538974657445888, 10276667637366784
OFFSET
0,2
COMMENTS
The corresponding denominators are 5^n.
EXAMPLE
n (5/(1 - i/2))^n
a(n) A370192(n)
0 1 +0 *i
1 4 -2 *i
2 12 -16 *i
3 16 -88 *i
4 -112 -384 *i
5 -1216 -1312 *i
6 -7488 -2816 *i
7 -35584 +3712 *i
8 -134912 +86016 *i
MATHEMATICA
LinearRecurrence[{8, -20}, {1, 4}, 26]
PROG
(PARI) a370191(n) = numerator(real(1/(1+I/2)^n))
CROSSREFS
Cf. A000351 (denominators), A370192.
Sequence in context: A361418 A066632 A038242 * A048661 A036047 A356812
KEYWORD
sign,frac,easy
AUTHOR
Hugo Pfoertner, Feb 17 2024
STATUS
approved