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

Author

Mohammad K. Azarian, Aug 21 2007

Keywords

• nonn

Links

• Harvey P. Dale, Table of n, a(n) for n = 0..1000

Crossrefs

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

Programs

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

Mathematica

Table[If[n>2&&PrimeQ[n],IntegerLength[n]Floor[n/10],n],{n,0,70}] (* Harvey P. Dale, Mar 31 2025 *)

Extensions

Offset changed by Mohammad K. Azarian, Nov 19 2008

Offset corrected by Robert Israel, Aug 04 2019