A045970 a(1)=7; if n = Product p_i^e_i, n > 1, then a(n) = Product p_{i+4}^e_i.

7, 11, 13, 121, 17, 143, 19, 1331, 169, 187, 23, 1573, 29, 209, 221, 14641, 31, 1859, 37, 2057, 247, 253, 41, 17303, 289, 319, 2197, 2299, 43, 2431, 47, 161051, 299, 341, 323, 20449, 53, 407, 377, 22627, 59, 2717, 61, 2783, 2873, 451, 67, 190333, 361, 3179, 403

Offset

1,1

References

From a puzzle proposed by Marc LeBrun.

Links

Table of n, a(n) for n=1..51.

Mathematica

f[p_, e_] := NextPrime[p, 4]^e; a[1] = 7; a[n_] := Times @@ f @@@ FactorInteger[n]; Array[a, 100] (* Amiram Eldar, Sep 19 2023 *)

Crossrefs

Cf. A045965, A045966, A045967, A045968, A045969, A045971, A045972, A045973.

Sequence in context: A288610 A062607 A018768 * A338597 A356455 A004235

Adjacent sequences: A045967 A045968 A045969 * A045971 A045972 A045973

Keyword

easy,nonn

Author

N. J. A. Sloane

Extensions

More terms from David W. Wilson

Status

approved