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A375906
Positions of primes in the sequence of numbers of the form 2^t * 3^u + 1 (A055600).
2
1, 2, 4, 5, 8, 9, 10, 14, 18, 20, 21, 24, 25, 28, 32, 33, 35, 38, 42, 43, 44, 51, 52, 54, 55, 68, 70, 75, 76, 87, 91, 95, 107, 108, 114, 122, 128, 134, 137, 138, 139, 142, 146, 150, 154, 156, 162, 176, 177, 187, 193, 198, 206, 214, 232, 234, 237, 242, 246, 248, 250
OFFSET
1,2
LINKS
FORMULA
A055600(a(n)) = A003586(a(n)) + 1 = A005109(n).
MATHEMATICA
With[{lim = 10^10}, Position[Sort@ Flatten@ Table[2^i*3^j + 1, {i, 0, Log2[lim]}, {j, 0, Log[3, lim/2^i]}], _?PrimeQ] // Flatten]
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(i, ", "))); }
CROSSREFS
KEYWORD
nonn
AUTHOR
Amiram Eldar, Sep 02 2024
STATUS
approved