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A077805
Smallest prime factor of numbers containing in their decimal representation only the digits 0 and 1.
3
1, 2, 11, 2, 101, 2, 3, 2, 7, 2, 3, 2, 3, 2, 11, 2, 73, 2, 3, 2, 3, 2, 10111, 2, 3, 2, 7, 2, 17, 2, 41, 2, 11, 2, 3, 2, 3, 2, 11, 2, 3, 2, 83, 2, 7, 2, 101111, 2, 3, 2, 11, 2, 23, 2, 149, 2, 11, 2, 31, 2, 241, 2, 3, 2, 101, 2, 3, 2, 3, 2, 7, 2, 3, 2, 11, 2, 971, 2, 181, 2, 3, 2, 31, 2, 73, 2
OFFSET
1,2
LINKS
FORMULA
a(n) = A020639(A007088(n)).
EXAMPLE
a(45) = A020639(A007088(45)) = A020639(101101) = A020639(7*11*13*101) = 7.
PROG
(PARI)
A007088(n) = fromdigits(binary(n), 10); \\ From A007088.
A020639(n) = if(1==n, n, factor(n)[1, 1]);
A077805(n) = A020639(A007088(n)); \\ Antti Karttunen, Feb 06 2019
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Reinhard Zumkeller, Nov 16 2002
STATUS
approved