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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
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
Sequence in context: A323068 A072627 A277144 * A194702 A118682 A198393
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 March 28 20:05 EDT 2024. Contains 371254 sequences. (Running on oeis4.)