A244149 a(n) = 2*(n*Denominator(((n-1)*(n^2)+2^(n+1)-4)/(2*n))-n)/n+1.

1, 1, 1, 3, 1, 5, 1, 7, 5, 9, 1, 11, 1, 13, 9, 15, 1, 17, 1, 19, 13, 21, 1, 23, 9, 25, 17, 3, 1, 29, 1, 31, 21, 33, 69, 35, 1, 37, 25, 39, 1, 41, 1, 43, 5, 45, 1, 47, 13, 49, 33, 51, 1, 53, 109, 55, 37, 57, 1, 59, 1, 61, 41, 63, 25, 65, 1, 67, 45, 9, 1, 71, 1, 73, 49, 75, 153, 77, 1, 79

Offset

1,4

Comments

Numbers n such that a(a(n + 1)) = 1: 1 U primes U pseudoprimes;

a(n) such that a(n - 1) = 1: 1 U 1 U odd primes U pseudoprimes.

Links

Table of n, a(n) for n=1..80.

Example

a(1) = (2*(1*Denominator(((1-1)*(1^2)+2^(1+1)-4)/(2*1))-1)/1+1 = 1.

Prog

(Magma) [2*(n*Denominator(((n-1)*(n^2)+2^(n+1)-4)/(2*n))-n)/n+1: n in [1..100]];
(PARI) a(n) = 2*(n*denominator(((n-1)*(n^2)+2^(n+1)-4)/(2*n))-n)/n + 1; \\ Michel Marcus, Sep 03 2014

Crossrefs

Cf. A000040, A001567, A015919, A065091.

Sequence in context: A160596 A092319 A254938 * A147410 A146623 A197943

Adjacent sequences: A244146 A244147 A244148 * A244150 A244151 A244152

Keyword

nonn

Author

Juri-Stepan Gerasimov, Sep 01 2014

Status

approved