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A210437
Greatest prime factor of reversal of digits of n.
3
1, 2, 3, 2, 5, 3, 7, 2, 3, 1, 11, 7, 31, 41, 17, 61, 71, 3, 13, 2, 3, 11, 2, 7, 13, 31, 3, 41, 23, 3, 13, 23, 11, 43, 53, 7, 73, 83, 31, 2, 7, 3, 17, 11, 3, 2, 37, 7, 47, 5, 5, 5, 7, 5, 11, 13, 5, 17, 19, 3, 2, 13, 3, 23, 7, 11, 19, 43, 3, 7, 17, 3, 37, 47, 19
OFFSET
1,2
LINKS
FORMULA
a(n) = A006530(A004086(n)) = gpf(R(n)). - Jonathan Vos Post, Mar 22 2012
MAPLE
with(numtheory):
r:= proc(n) option remember; local q;
`if`(n<10, n, irem(n, 10, 'q')*10^(length(n)-1) +r(q))
end:
a:= n-> `if`(r(n)=1, 1, max(factorset(r(n))[])):
seq(a(n), n=1..100);
MATHEMATICA
FactorInteger[FromDigits[Reverse[IntegerDigits[#]]]][[-1, 1]]&/@Range[80] (* Harvey P. Dale, Sep 14 2014 *)
PROG
(PARI) gpf(n) = if (n==1, 1, vecmax(factor(n)[, 1]));
a(n) = gpf(fromdigits(Vecrev(digits(n)))); \\ Michel Marcus, Feb 11 2020
CROSSREFS
KEYWORD
nonn,look,base
AUTHOR
Alois P. Heinz, Mar 21 2012
STATUS
approved