A088379 a(n) = (smallest prime factor of n)^4; a(1) = 1.

1, 16, 81, 16, 625, 16, 2401, 16, 81, 16, 14641, 16, 28561, 16, 81, 16, 83521, 16, 130321, 16, 81, 16, 279841, 16, 625, 16, 81, 16, 707281, 16, 923521, 16, 81, 16, 625, 16, 1874161, 16, 81, 16, 2825761, 16, 3418801, 16, 81, 16, 4879681, 16, 2401, 16

Offset: 1

Author

Reinhard Zumkeller, Sep 28 2003

Keywords

• nonn
• easy

Links

• Eric Weisstein's World of Mathematics, Biquadratic Number.
• Eric Weisstein's World of Mathematics, Least Prime Factor.

Crossrefs

Cf. A020639, A000583, A088377, A088378.

Programs

Mathematica

a[n_] := FactorInteger[n][[1, 1]]^4; Array[a, 100] (* Amiram Eldar, May 16 2025 *)

PARI

a(n) = if(n == 1, 1, factor(n)[1,1]^4); \\ Amiram Eldar, May 16 2025

Formula

a(n) = A000583(A020639(n)).

a(n) = A088377(n)^2. - Amiram Eldar, May 16 2025