A077805 Smallest prime factor of numbers containing in their decimal representation only the digits 0 and 1.

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

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: A347121 A341512 A276676 * A344539 A342043 A351997

Adjacent sequences: A077802 A077803 A077804 * A077806 A077807 A077808

Keyword

nonn,base

Author

Reinhard Zumkeller, Nov 16 2002

Status

approved