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
Keywords
Links
- Harvey P. Dale, Table of n, a(n) for n = 0..1000
Programs
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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