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A322780
First differences of A237262.
3
1, 4, 9, 32, 71, 252, 559, 1984, 4401, 15620, 34649, 122976, 272791, 968188, 2147679, 7622528, 16908641, 60012036, 133121449, 472473760, 1048062951, 3719778044, 8251382159, 29285750592, 64962994321, 230566226692, 511452572409, 1815244062944
OFFSET
1,2
FORMULA
From Colin Barker, Jan 06 2019: (Start)
G.f.: x*(1 + 4*x + x^2) / (1 - 8*x^2 + x^4).
a(n) = 8*a(n-2) - a(n-4) for n>4.
(End)
PROG
(PARI) Vec(x*(1 + 4*x + x^2) / (1 - 8*x^2 + x^4) + O(x^40)) \\ Colin Barker, Jan 06 2019
CROSSREFS
Sequence in context: A324020 A265645 A005985 * A343547 A151271 A149115
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, Jan 05 2019, following a suggestion from Stan Wagon.
STATUS
approved