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A005166 a(0) = 1; a(n) = (1 + a(0)^3 + ... + a(n-1)^3)/n (not always integral!).
(Formerly M1551)
6
1, 2, 5, 45, 22815, 2375152056927, 2233176271342403475345148513527359103 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Terms are integer until n=A097398(2,2)=89.

Guy states that by computing the sequence modulo 89 it is easy to show that a(89) is not integral. - T. D. Noe, Sep 17 2007

REFERENCES

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=0..9

R. K. Guy, Letter to N. J. A. Sloane, Sep 25 1986.

R. K. Guy, The strong law of small numbers. Amer. Math. Monthly 95 (1988), no. 8, 697-712.

R. K. Guy, The strong law of small numbers. Amer. Math. Monthly 95 (1988), no. 8, 697-712. [Annotated scanned copy]

N. Lygeros & M. Mizony, Study of primality of terms of a_k(n)=(1+(sum from 1 to n-1)(a_k(i)^k))/(n-1)  [dead link]

Eric Weisstein's World of Mathematics, Goebel's Sequence.

CROSSREFS

Cf. A003504, A005167.

Cf. A108394

Sequence in context: A334252 A307147 A056680 * A121621 A225147 A119715

Adjacent sequences:  A005163 A005164 A005165 * A005167 A005168 A005169

KEYWORD

nonn,easy,nice

AUTHOR

N. J. A. Sloane.

STATUS

approved

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Last modified July 14 22:44 EDT 2020. Contains 335738 sequences. (Running on oeis4.)