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A069850
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Number of distinct primes obtained by inserting a 9 at all possible places in n. This includes prefixing as well as suffixing.
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10
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1, 1, 0, 0, 1, 0, 2, 1, 0, 1, 2, 0, 2, 1, 0, 0, 2, 0, 2, 0, 0, 1, 2, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 1, 1, 0, 3, 1, 0, 1, 3, 0, 1, 1, 0, 0, 2, 0, 1, 1, 0, 0, 2, 0, 0, 1, 0, 0, 1, 0, 2, 0, 0, 0, 1, 0, 1, 0, 0, 1, 2, 0, 1, 0, 0, 1, 2, 0, 0, 1, 0, 1, 2, 0, 1, 0, 0, 0, 0, 0, 2, 1, 0, 0, 0, 0, 1, 0, 0, 1, 3, 0, 3, 1, 0
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OFFSET
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1,7
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LINKS
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EXAMPLE
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MAPLE
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f:= proc(n) local k;
if member(n mod 10, {0, 2, 4, 5, 6, 8}) then if isprime(10*n+9) then return 1 else return 0 fi fi;
nops(select(isprime, {seq(9*10^k + 10^(k+1)*floor(n/10^k) + (n mod 10^k), k=0..ilog10(n)+1)}));
end proc:
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MATHEMATICA
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Table[ Count[ PrimeQ[ Union[ FromDigits /@ Table[ Insert[ IntegerDigits[n], 9, j], {j, 1, Floor[ Log[10, n] + 2]}]]], True], {n, 1, 105}]
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CROSSREFS
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KEYWORD
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base,nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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