

A076565


Greatest prime divisor of 2n+1 (sum of two successive integers).


6



3, 5, 7, 3, 11, 13, 5, 17, 19, 7, 23, 5, 3, 29, 31, 11, 7, 37, 13, 41, 43, 5, 47, 7, 17, 53, 11, 19, 59, 61, 7, 13, 67, 23, 71, 73, 5, 11, 79, 3, 83, 17, 29, 89, 13, 31, 19, 97, 11, 101, 103, 7, 107, 109, 37, 113, 23, 13, 17, 11, 41, 5, 127, 43, 131, 19, 5, 137, 139, 47, 13
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OFFSET

1,1


LINKS

Robert Israel, Table of n, a(n) for n = 1..10000


FORMULA

a(n) = A006530(2n+1).  Robert Israel, Mar 17 2017


MAPLE

seq(max(numtheory:factorset(2*n+1)), n=1..200); # Robert Israel, Mar 17 2017


MATHEMATICA

Table[FactorInteger[2n + 1][[1, 1]], {n, 1, 100}] (* Indranil Ghosh, Mar 20 2017 *)


PROG

(PARI) for(n=1, 100, print1(vecmax(factor(2*n + 1)[, 1]), ", ")) \\ Indranil Ghosh, Mar 20 2017
(Python)
from sympy.ntheory import primefactors
print [max(primefactors(2*n + 1)) for n in range(1, 101)] # Indranil Ghosh, Mar 20 2017


CROSSREFS

Cf. A006530
Sequence in context: A090368 A120374 A088836 * A286517 A199423 A100029
Adjacent sequences: A076562 A076563 A076564 * A076566 A076567 A076568


KEYWORD

easy,nonn


AUTHOR

Zak Seidov, Oct 19 2002


STATUS

approved



