A291530 a(n) is the smallest k such that uphi(k*n) = uphi(k*n+1), or 0 if no such k exists.

1, 10, 373, 5, 4, 372, 5, 26, 248, 2, 13, 186, 11, 562, 247, 13, 627, 124, 195, 1, 183, 86, 245, 93, 5184, 8, 185, 281, 1623, 4320, 72, 738, 43, 2296, 1, 62, 20, 2312, 95, 3240, 576, 732, 33, 43, 111, 4600, 540100, 492, 115, 2592, 209, 4, 25383, 2388, 629, 549, 65, 1732, 64476, 2160, 20, 36, 61

Offset: 1

Author

Altug Alkan, Aug 25 2017

Keywords

• nonn

Examples

			a(3) = 373 because uphi(373*3) = uphi(373*3+1) and 373 is the smallest number with this property.
		

Crossrefs

Cf. A047994, A275412, A287055.

Programs

PARI

uphi(n) = my(f=factor(n)); prod(i=1, #f~, f[i, 1]^f[1, 2]-1);
a(n) = {my(k = 1); while (uphi(k*n) != uphi(k*n+1), k++); k; }