

A221183


a(0)=0, a(1)=1; thereafter a(n) = gpf(2*a(n1)+a(n2)), where gpf = "greatest prime factor" (A006530).


1



0, 1, 2, 5, 3, 11, 5, 7, 19, 5, 29, 7, 43, 31, 7, 5, 17, 13, 43, 11, 13, 37, 29, 19, 67, 17, 101, 73, 19, 37, 31, 11, 53, 13, 79, 19, 13, 5, 23, 17, 19, 11, 41, 31, 103, 79, 29, 137, 101, 113, 109, 331, 257, 13, 283, 193, 223, 71, 73, 31, 5, 41, 29, 11, 17, 5, 3, 11, 5, 7, 19, 5, 29, 7, 43, 31, 7, 5, 17
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OFFSET

0,3


COMMENTS

Rapidly enters a loop of length 62: [5, 3, 11, 5, 7, 19, 5, 29, 7, 43, 31, 7, 5, 17, 13, 43, 11, 13, 37, 29, 19, 67, 17, 101, 73, 19, 37, 31, 11, 53, 13, 79, 19, 13, 5, 23, 17, 19, 11, 41, 31, 103, 79, 29, 137, 101, 113, 109, 331, 257, 13, 283, 193, 223, 71, 73, 31, 5, 41, 29, 11, 17].


LINKS

Table of n, a(n) for n=0..78.
Greg Back and Mihai Caragiu, The Greatest Prime Factor and Recurrent Sequences, Fibonacci Quart. 48 (2010), no. 4, 358362. [Discusses similar sequences]


PROG

(PARI) gpf(n) = if (n==1, 1, vecmax(factor(n)[, 1]));
lista(nn) = {print1(x=0, ", "); print1(y=1, ", "); for (n=2, nn, z = gpf(x+2*y); print1(z, ", "); x = y; y = z; ); } \\ Michel Marcus, Mar 01 2016


CROSSREFS

Cf. A006530, A175723.
Sequence in context: A091809 A110315 A275677 * A178174 A094744 A229608
Adjacent sequences: A221180 A221181 A221182 * A221184 A221185 A221186


KEYWORD

nonn


AUTHOR

Gary W. Adamson and N. J. A. Sloane, Jan 19 2013


STATUS

approved



