A122262 Number of numbers having only factors that are Pierpont primes.

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 20, 20, 21, 22, 23, 24, 25, 25, 26, 26, 27, 27, 28, 29, 30, 31, 32, 33, 34, 34, 35, 35, 35, 36, 36, 36, 37, 38, 39, 40, 41, 41, 42, 42, 43, 44, 44, 44, 45, 45, 45, 46, 47, 48, 48, 48, 49, 49, 50, 50, 51

Offset

1,2

Links

Table of n, a(n) for n=1..72.

Eric Weisstein's World of Mathematics, Pierpont Prime.

Mathematica

smooth3Q[n_] := Times @@ ({2, 3}^IntegerExponent[n, {2, 3}]) == n; s[n_] := Boole@ AllTrue[FactorInteger[n][[;; , 1]]-1, smooth3Q]; s[1] = 1; Accumulate[Table[s[n], {n, 1, 100}]] (* Amiram Eldar, May 14 2025 *)

Crossrefs

Partial sums of A122261.

Cf. A005109.

Sequence in context: A337769 A061069 A122256 * A172268 A017895 A228722

Adjacent sequences: A122259 A122260 A122261 * A122263 A122264 A122265

Keyword

nonn

Author

Reinhard Zumkeller, Aug 29 2006

Status

approved