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

1,1

Links

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

Example

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 .

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);

Crossrefs

Cf. A001414, A065925.

Sequence in context: A185341 A067843 A245942 * A316707 A109360 A141622

Adjacent sequences: A280940 A280941 A280942 * A280944 A280945 A280946

Keyword

nonn,easy

Author

Paolo P. Lava, Jan 11 2017

Status

approved