A069843 Number of distinct primes obtained by inserting a 2 at all possible places in n. This includes prefixing.

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

Offset

1,41

Links

Table of n, a(n) for n=1..105.

Example

See the example in A069842.

Mathematica

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

Crossrefs

Cf. A069842, A069844, A069845, A069846, A069847, A069848, A069849, A069850 and A069851.

Sequence in context: A241541 A086008 A083910 * A069849 A138045 A072507

Adjacent sequences: A069840 A069841 A069842 * A069844 A069845 A069846

Keyword

base,nonn

Author

Amarnath Murthy, Apr 16 2002

Extensions

Edited and extended by Robert G. Wilson v, Apr 18 2002

a(17) corrected by Georg Fischer, Apr 19 2022

Status

approved