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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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..16384

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

Cf. A007088, A020639, A077806, A020449.

Sequence in context: A329941 A341512 A276676 * A342043 A104662 A333861

Adjacent sequences:  A077802 A077803 A077804 * A077806 A077807 A077808

KEYWORD

nonn,base

AUTHOR

Reinhard Zumkeller, Nov 16 2002

STATUS

approved

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Last modified May 16 19:46 EDT 2021. Contains 343951 sequences. (Running on oeis4.)