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A376701
The values of j in primes of the form 2^i*3^j - 1 (A005105) in the order of their appearance.
3
1, 0, 1, 0, 1, 2, 1, 0, 1, 3, 2, 3, 0, 1, 1, 3, 4, 3, 5, 2, 4, 7, 1, 3, 0, 7, 8, 5, 6, 3, 5, 2, 0, 7, 4, 2, 9, 3, 10, 5, 0, 1, 5, 12, 9, 4, 7, 2, 13, 10, 15, 5, 6, 4, 13, 8, 17, 0, 15, 5, 12, 6, 13, 20, 3, 7, 9, 4, 5, 14, 1, 9, 16, 15, 17, 11, 23, 13, 10, 1, 7, 7, 3, 19, 16, 3
OFFSET
1,6
LINKS
FORMULA
a(n) = A007949(A005105(n)+1).
MATHEMATICA
With[{lim = 10^13}, IntegerExponent[Select[Sort@ Flatten@Table[2^i*3^j - 1, {i, 0, Log2[lim]}, {j, 0, Log[3, lim/2^i]}], PrimeQ] + 1, 3]]
PROG
(PARI) lista(lim) = {my(s = List()); for(i = 0, logint(lim, 2), for(j = 0, logint(lim >> i, 3), listput(s, 2^i * 3^j - 1))); s = Set(s); for(i = 1, #s, if(isprime(s[i]), print1(valuation(s[i] + 1, 3), ", "))); }
CROSSREFS
KEYWORD
nonn
AUTHOR
Amiram Eldar, Oct 02 2024
STATUS
approved