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A275320
Least k such that d(k*n) = d(k*n+1) where d = A000005, or -1 if no such k exists.
1
2, 1, 7, 11, 15, 229, 2, 13, 15, 23, 3, 277, 2, 1, 5, 122, 2, 313, 2, 127, 1, 2, 10, 401, 3, 1, 5, 71, 4, 829, 3, 61, 1, 1, 21, 1259, 8, 1, 11, 137, 5, 1667, 2, 1, 3, 5, 2, 2038, 2, 241, 13, 2, 27, 331, 23, 94, 1, 2, 2, 5689, 2, 7, 3, 146, 17, 569, 3, 67, 15, 491, 2, 1487, 14, 4, 1
OFFSET
1,1
COMMENTS
There are infinitely many 1's in this sequence. See comments section of A005237.
LINKS
FORMULA
a(A005237(n)) = 1.
EXAMPLE
a(4) = 11 because A000005(4*11) = A000005(4*11+1).
MAPLE
f:= proc(n)
local k;
for k from 1 do if numtheory:-tau(n*k) = numtheory:-tau(n*k+1) then return k fi od:
end proc:
map(f, [$1..100]); # Robert Israel, Aug 01 2016
PROG
(PARI) a(n) = {my(k = 1); while (numdiv(k*n) != numdiv(k*n+1), k++); k; }
CROSSREFS
Sequence in context: A203991 A075118 A100245 * A272931 A095137 A239104
KEYWORD
nonn
AUTHOR
Altug Alkan, Jul 27 2016
STATUS
approved