A069850 Number of distinct primes obtained by inserting a 9 at all possible places in n. This includes prefixing as well as suffixing.

1, 1, 0, 0, 1, 0, 2, 1, 0, 1, 2, 0, 2, 1, 0, 0, 2, 0, 2, 0, 0, 1, 2, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 1, 1, 0, 3, 1, 0, 1, 3, 0, 1, 1, 0, 0, 2, 0, 1, 1, 0, 0, 2, 0, 0, 1, 0, 0, 1, 0, 2, 0, 0, 0, 1, 0, 1, 0, 0, 1, 2, 0, 1, 0, 0, 1, 2, 0, 0, 1, 0, 1, 2, 0, 1, 0, 0, 0, 0, 0, 2, 1, 0, 0, 0, 0, 1, 0, 0, 1, 3, 0, 3, 1, 0

Offset

1,7

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Example

See the example in A069842.

Maple

f:= proc(n) local k;
  if member(n mod 10, {0, 2, 4, 5, 6, 8}) then if isprime(10*n+9) then return 1 else return 0 fi fi;
  nops(select(isprime, {seq(9*10^k + 10^(k+1)*floor(n/10^k) + (n mod 10^k), k=0..ilog10(n)+1)}));
end proc:
map(f, [$1..200]); # Robert Israel, Oct 09 2020

Mathematica

Table[ Count[ PrimeQ[ Union[ FromDigits /@ Table[ Insert[ IntegerDigits[n], 9, j], {j, 1, Floor[ Log[10, n] + 2]}]]], True], {n, 1, 105}]

Crossrefs

Cf. A069842, A069843, A069844, A069845, A069846, A069847, A069848, A069849 and A069851.

Sequence in context: A244422 A061896 A366793 * A141581 A179286 A193690

Adjacent sequences: A069847 A069848 A069849 * A069851 A069852 A069853

Keyword

base,nonn

Author

Amarnath Murthy, Apr 16 2002

Extensions

More terms from Vladeta Jovovic, Apr 17 2002

Edited by Robert G. Wilson v, Apr 18 2002

Status

approved