A280943 Least number k such that sopfr(k) = sopfr(k + n), where sopfr(k) is the integer log of k.

5, 10, 7, 20, 7, 14, 20, 40, 13, 14, 21, 28, 14, 40, 19, 33, 11, 26, 56, 28, 49, 42, 115, 56, 35, 28, 31, 57, 11, 38, 50, 66, 63, 11, 17, 52, 11, 112, 42, 51, 22, 98, 11, 84, 57, 35, 52, 95, 138, 13, 33, 56, 22, 62, 77, 114, 61, 22, 39, 76, 44, 13, 91, 57, 70

Offset: 1

Author

Paolo P. Lava, Jan 11 2017

Keywords

• nonn
• easy

Examples

			a(1) = 5 because 5 is the least number such that sopfr(5) = sopfr(5 + 1) = 5 .
a(2) = 10 because 10 is the least number such that sopfr(10) = sopfr(10 + 2) = 7 .
		

Links

• Paolo P. Lava, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A001414, A065925.

Programs

Maple

with(numtheory):P:=proc(q) local a,b,k,n; for n from 1 to q do for k from 1 to q do
a:=ifactors(k)[2]; b:=ifactors(k+n)[2];
if add(a[k][1]*a[k][2],k=1..nops(a))=add(b[k][1]*b[k][2],k=1..nops(b))
then print(k); break; fi; od; od; end: P(10^9);