A113972 Define b(0)=28, b(n+1)=2*b(n)+1; sequence gives largest prime factor of b(n).

7, 19, 23, 11, 463, 103, 53, 1237, 571, 101, 5939, 6599, 239, 313, 95027, 1223, 1900543, 281, 43441, 1699, 2339131, 2896067, 1283, 3229, 3021983, 5317369, 389231411, 32869, 301999, 2339, 2154169, 98383927, 25015877, 340939

Offset

0,1

Comments

a(k) = 29*2^k-1 for k in A050540. - Robert Israel, Nov 23 2016

Links

Robert Israel, Table of n, a(n) for n = 0..250

Formula

a(n) = A006530(29*2^n-1). - Robert Israel, Nov 23 2016

Example

a(2)=23 because b(1) = 2*28 + 1 = 57 and b(2) = 2*57 + 1 = 115 = 5*23.

Maple

with(numtheory): b:=proc(n): if n=0 then 28 else 2*b(n-1)+1 fi: end: a:=proc(n) local bb: bb:=factorset(b(n)): bb[nops(bb)] end: seq(a(n), n=0..38); # Emeric Deutsch, May 14 2006

Crossrefs

Cf. A006530, A050540.

Sequence in context: A125265 A023152 A123532 * A082422 A129812 A353046

Adjacent sequences: A113969 A113970 A113971 * A113973 A113974 A113975

Keyword

nonn

Author

Bill McEachen, Feb 06 2006

Extensions

More terms from Emeric Deutsch, May 14 2006

Status

approved