A337395 a(n) is the largest exponent k such that the sums, with multiplicity, of the i-th powers of the prime factors of A100118(n) are all prime for i=1 to k.

1, 1, 1, 2, 1, 2, 1, 6, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 9, 1, 1, 4, 1, 1, 1, 1, 3, 3, 1, 1, 1, 3, 1, 1, 1, 3, 1, 1, 3, 1, 1, 1, 1, 2, 3, 1, 2, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 2, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1

Offset

1,4

Links

Table of n, a(n) for n=1..88.

Example

a(4) = 2 because (2^1) + (3^1) = 5 and (2^2) + (3^2) = 13.
a(6) = 2 because (2^1) + (5^1) = 7 and (2^2) + (5^2) = 29.
a(8) = 6 because (2^1) + (2^1) + (3^1) = 7 and (2^2) + (2^2) + (3^2) = 17 and (2^3) + (2^3) + (3^3) = 43 and (2^4) + (2^4) + (3^4) = 113 and (2^5) + (2^5) + (3^5) = 307 and (2^6) + (2^6) + (3^6) = 857.

Prog

(PARI) a(n) = {my(f=factor(n), x = 1, y = 1); while(y, if(isprime(sum(i=1, #f~, f[i, 1]^x*f[i, 2])), x++, y = 0)); return(x - 1)}
for (n = 2, 220, if(a(n) > 0, print1(a(n), ", ")))

Crossrefs

Cf. A001414, A100118.

Cf. A067666, A224787.

Sequence in context: A152823 A324605 A086545 * A126083 A356158 A071416

Adjacent sequences: A337392 A337393 A337394 * A337396 A337397 A337398

Keyword

nonn

Author

Torlach Rush, Aug 25 2020

Status

approved