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Number of distinct primes obtained by inserting a 2 at all possible places in n. This includes prefixing.
9

%I #8 Apr 19 2022 07:23:40

%S 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,

%T 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,

%U 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

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

%e See the example in A069842.

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

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

%K base,nonn

%O 1,41

%A _Amarnath Murthy_, Apr 16 2002

%E Edited and extended by _Robert G. Wilson v_, Apr 18 2002

%E a(17) corrected by _Georg Fischer_, Apr 19 2022