A229767 Largest prime factor of 2^(2*n+1)-2^(n+1)+1.

5, 5, 113, 37, 397, 1613, 61, 953, 457, 14449, 30269, 8101, 246241, 107367629, 384773, 312709, 47392381, 184481113, 1249, 12112549, 1759217765581, 54001, 140737471578113, 4981857697937, 26317, 1801439824104653, 415878438361, 525313, 174877, 368140581013

Offset

1,1

Comments

2^(2*n+1)-2^(n+1)+1 is a factor of 4^(2*n+1)+1.

Links

Daniel Suteu, Table of n, a(n) for n = 1..547

Example

For n=5, 2^(2*n+1)-2^(n+1)+1 = 1985 = 5*397, so a(5)=397.

Prog

(PARI) a(n) = {f=factor(2^(2*n+1)-2^(n+1)+1); f[matsize(f)[1], 1]}

Crossrefs

Cf. A092440, A207262, A229747, A229768.

Sequence in context: A081050 A081049 A048607 * A369753 A215729 A364452

Adjacent sequences: A229764 A229765 A229766 * A229768 A229769 A229770

Keyword

nonn

Author

Colin Barker, Sep 29 2013

Status

approved