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A069848 Number of distinct primes obtained by inserting a 7 at all possible places in n. This includes prefixing as well as suffixing. 9

%I #4 Dec 05 2013 19:55:18

%S 2,0,2,1,0,1,0,0,2,1,0,1,2,0,1,1,0,0,3,0,1,1,0,0,1,0,2,0,0,1,1,0,3,1,

%T 0,1,0,0,3,0,0,0,1,0,1,1,0,1,1,0,2,0,0,1,1,0,2,1,0,1,2,0,1,1,0,0,1,0,

%U 1,0,0,1,1,0,1,0,0,1,1,0,0,1,0,0,1,0,2,1,0,1,1,0,1,1,0,1,2,0,1,0,0,0,1,0,0

%N Number of distinct primes obtained by inserting a 7 at all possible places in n. This includes prefixing as well as suffixing.

%e See the example in A069842.

%t Table[ Count[ PrimeQ[ Union[ FromDigits /@ Table[ Insert[ IntegerDigits[n], 7, j], {j, 1, Floor[ Log[10, n] + 2]}]]], True], {n, 1, 105}]

%Y Cf. A069842, A069843, A069844, A069845, A069846, A069847, A069849, A069850 and A069851.

%K base,nonn

%O 1,1

%A _Amarnath Murthy_, Apr 16 2002

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

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Last modified March 28 13:35 EDT 2024. Contains 371254 sequences. (Running on oeis4.)