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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
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, 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, 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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

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], 7, j], {j, 1, Floor[ Log[10, n] + 2]}]]], True], {n, 1, 105}]

CROSSREFS

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

Sequence in context: A323068 A072627 A277144 * A194702 A118682 A198393

Adjacent sequences:  A069845 A069846 A069847 * A069849 A069850 A069851

KEYWORD

base,nonn

AUTHOR

Amarnath Murthy, Apr 16 2002

EXTENSIONS

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

STATUS

approved

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Last modified April 21 23:52 EDT 2021. Contains 343156 sequences. (Running on oeis4.)