A130891 a(n) = n if n is not an odd prime number. Otherwise, a(n) = k*floor(n/10), where k is the smallest integer such that n < 10^k.

0, 1, 2, 0, 4, 0, 6, 0, 8, 9, 10, 2, 12, 2, 14, 15, 16, 2, 18, 2, 20, 21, 22, 4, 24, 25, 26, 27, 28, 4, 30, 6, 32, 33, 34, 35, 36, 6, 38, 39, 40, 8, 42, 8, 44, 45, 46, 8, 48, 49, 50, 51, 52, 10, 54, 55, 56, 57, 58, 10, 60, 12, 62, 63, 64, 65, 66, 12, 68

Offset

0,3

Links

Table of n, a(n) for n=0..68.

Maple

f:= proc(n) local k;
  if n::odd and isprime(n) then
    k:= ilog10(n)+1;
    k*floor(n/10)
  else n
  fi
end proc:
map(f, [$0..100]); # Robert Israel, Aug 04 2019

Crossrefs

Cf. A131516, A130758, A000027, A001477, A006005.

Sequence in context: A071648 A001613 A237420 * A091371 A144775 A249744

Adjacent sequences: A130888 A130889 A130890 * A130892 A130893 A130894

Keyword

nonn

Author

Mohammad K. Azarian, Aug 21 2007

Extensions

Offset changed by Mohammad K. Azarian, Nov 19 2008

Offset corrected by Robert Israel, Aug 04 2019

Status

approved