A129871 - OEIS (original) (raw)

COMMENTS

A variant of A000058, starting with an extra 1.

REFERENCES

Jean-Marie Monier, Analyse, Exercices corrigés, 2ème année, MP, Dunod, 1997, Exercice 3.3.4 page 284.

FORMULA

For n>0, a(n) = A000058(n-1).

a(1) = 2, a(n+1) = a(n)^2 - a(n) + 1. a(n) = round(c^(2^n)), where c = 1.264... is the Vardi constant, A076393. - Thomas Ordowski, Jun 11 2013

Sum_{n>=0} 1/a(n) = 2.

Sum_{n>=0} (-1)^(n+1)/a(n) = 2 * (A118227 - 1). (End)

MATHEMATICA

a[0] = 1; a[n_] := a[n] = Product[a[k], {k, 0, n - 1}] + 1

PROG

(Haskell)

a129871 n = a129871_list !! n

CROSSREFS

Cf. A000058 which is the main entry for this sequence.