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A340259 a(n) = A340312(n, 2^(n-1)). a(n) is the central term of row n of A340312. 2
1, 0, 14, 870, 18796230, 28634752793916486, 187118328452563149209991044344449606, 22533823529098462258163079522899558179092788838542277982316450977506091590 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

a(9) = 2299131884087642202247291403507120751687796592498104258 * C, where C is a composite factor with 96 digits.

C = P47*P49, with P47 = 88967307877356450624418823383132738084943851019 and

P49 = 4512180962860489443011495305279720577473472225641. - Hugo Pfoertner, Jan 09 2021

LINKS

Andrew Howroyd, Table of n, a(n) for n = 1..11

FORMULA

a(n) = (2*binomial(2^n-1, 2^(n-1)) + (2^n-1)*binomial(2^(n-1), 2^(n-2)))/2^n for n >= 3. - Andrew Howroyd, Jan 09 2021

MAPLE

seq(A340312_row(n)[2^(n-1)+1], n = 1..8);

PROG

(PARI) a(n) = {if(n<=2, n==1, (2*binomial(2^n-1, 2^(n-1)) + (2^n-1)*binomial(2^(n-1), 2^(n-2)))/2^n)} \\ Andrew Howroyd, Jan 09 2021

CROSSREFS

Cf. A340312, A340263.

Sequence in context: A064345 A269335 A159871 * A269610 A115458 A241801

Adjacent sequences:  A340256 A340257 A340258 * A340260 A340261 A340262

KEYWORD

nonn

AUTHOR

Peter Luschny, Jan 06 2021

STATUS

approved

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Last modified May 14 07:13 EDT 2021. Contains 343879 sequences. (Running on oeis4.)