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A073587 a(n)=a(n-1)*2^n+1 where a(0)=1. 4
1, 3, 13, 105, 1681, 53793, 3442753, 440672385, 112812130561, 57759810847233, 59146046307566593, 121131102837896382465, 496152997224023582576641, 4064485353259201188467843073, 66592528027798752271857140908033 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Also, number of nodes in an n-ary tree with increasing fanout as the level increases. - Dhruv Matani, Apr 12 2012

LINKS

Table of n, a(n) for n=0..14.

FORMULA

a(n) = floor(D*2^(n*(n+1)/2)) where D is a constant, D=1.64163256065515386629...=sum(k>=0, 1/2^(k(k+1)/2)) - Benoit Cloitre, Sep 01 2002

MATHEMATICA

a = 1; Table[a = a*2^n + 1, {n, 14}] (* Jayanta Basu, Jul 02 2013 *)

PROG

(UBASIC)

25 A=1

30 for I=1 to 20

40 A=A*2^I+1

50 print A

60 next

70 end

CROSSREFS

Cf. A000225 (nodes in a binary tree).

Sequence in context: A228148 A098027 A182104 * A333736 A220704 A061377

Adjacent sequences:  A073584 A073585 A073586 * A073588 A073589 A073590

KEYWORD

easy,nonn

AUTHOR

Felice Russo, Aug 28 2002

EXTENSIONS

Added a(0)=1. Added information from duplicate sequence A182104. - N. J. A. Sloane, Dec 28 2015

STATUS

approved

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Last modified July 14 10:07 EDT 2020. Contains 335721 sequences. (Running on oeis4.)