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A002021 Pile of coconuts problem: (n-1)(n^n - 1), n even; n^n - n + 1, n odd.
(Formerly M3114 N1262)
5
1, 3, 25, 765, 3121, 233275, 823537, 117440505, 387420481, 89999999991, 285311670601, 98077104930805, 302875106592241, 144456088732254195, 437893890380859361, 276701161105643274225, 827240261886336764161, 668888937280041138782191, 1978419655660313589123961 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

REFERENCES

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

LINKS

T. D. Noe, Table of n, a(n) for n = 1..100

Santo D'Agostino, “The Coconut Problem”; Updated With Solution, May 2011.

R. S. Underwood and Robert E. Moritz, Problem 3242, Amer. Math. Monthly, 35 (1928), 47-48.

Ben Ames Williams, Coconuts Problem

R. G. Wilson, V, Letter to N. J. A. Sloane, Oct. 1993

FORMULA

E.g.f.: (1-x)*exp(x)-(W(x)+2)*(2*W(x)+1)/(2*(1+W(x))^3)-W(-x)/(2*(1+W(-x))^3) where W is the Lambert W function. - Robert Israel, Aug 26 2016

MAPLE

seq(`if`(n::even, (n-1)*(n^n - 1), n^n-n+1), n=1..30); # Robert Israel, Aug 26 2016

MATHEMATICA

Table[If[EvenQ[n], (n-1)(n^n-1), n^n-n+1], {n, 30}] (* Harvey P. Dale, Apr 21 2012 *)

CROSSREFS

Cf. A002022, A006091.

Sequence in context: A127231 A062411 A136516 * A322063 A306792 A012764

Adjacent sequences:  A002018 A002019 A002020 * A002022 A002023 A002024

KEYWORD

easy,nonn,nice

AUTHOR

N. J. A. Sloane

EXTENSIONS

More terms from Harvey P. Dale, Apr 21 2012

STATUS

approved

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Last modified December 15 00:30 EST 2019. Contains 329988 sequences. (Running on oeis4.)