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A209190 Least prime factor of reversal of digits of n. 3
1, 2, 3, 2, 5, 2, 7, 2, 3, 1, 11, 3, 31, 41, 3, 61, 71, 3, 7, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 13, 23, 3, 43, 53, 3, 73, 83, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 5, 3, 5, 5, 3, 5, 5, 3, 5, 5, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 7, 17, 3, 37, 47, 3, 67, 7, 3, 97, 2, 2, 2 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
This is to lpf (A020639) as A210437 is to gpf (A006530). - Jonathan Vos Post, Mar 22 2012
LINKS
FORMULA
a(n) = A020639(A004086(n)) = lpf(R(n)). - Jonathan Vos Post, Mar 22 2012
MAPLE
read("transforms") ;
A209190 := proc(n)
A020639(digrev(n)) ;
end proc:
seq(A209190(n), n=1..100) ; # R. J. Mathar, Mar 22 2012
MATHEMATICA
a[n_] := FactorInteger[IntegerReverse[n]][[1, 1]];
Array[a, 100] (* Jean-François Alcover, Jan 14 2021 *)
PROG
(PARI) lpf(n) = if (n==1, 1, vecmin(factor(n)[, 1]));
a(n) = lpf(fromdigits(Vecrev(digits(n)))); \\ Michel Marcus, Feb 11 2020
CROSSREFS
Sequence in context: A284694 A072591 A085308 * A086286 A272565 A135679
KEYWORD
nonn,base,look
AUTHOR
N. J. A. Sloane, Mar 05 2012
STATUS
approved

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Last modified March 29 09:14 EDT 2024. Contains 371268 sequences. (Running on oeis4.)