A062312 Nonprime numbers squared.

1, 16, 36, 64, 81, 100, 144, 196, 225, 256, 324, 400, 441, 484, 576, 625, 676, 729, 784, 900, 1024, 1089, 1156, 1225, 1296, 1444, 1521, 1600, 1764, 1936, 2025, 2116, 2304, 2401, 2500, 2601, 2704, 2916, 3025, 3136, 3249, 3364, 3600, 3844, 3969, 4096, 4225

Offset: 1

Author

Jason Earls, Jul 05 2001

Keywords

• easy
• nonn

Links

• Harry J. Smith, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A002808, A018252, A275647.

Programs

Mathematica

Select[Range[100],!PrimeQ[#]&]^2 (* Harvey P. Dale, Jan 27 2016 *)

PARI

for(n=1,30, if(isprime(n), n+1,print(n^2)))

PARI

n=0; for (m=1, 2000, if (!isprime(m), write("b062312.txt", n++, " ", m^2); if (n==1000, break))) \\ Harry J. Smith, Aug 04 2009

PARI

is(n)=issquare(n,&n) && !isprime(n) \\ Charles R Greathouse IV, Sep 18 2015

Formula

a(n) = A018252(n)^2. - Omar E. Pol, Oct 30 2007

Sum_{n>=1} 1/a(n) = A275647. - Amiram Eldar, Oct 14 2020

Extensions

More terms from Larry Reeves (larryr(AT)acm.org), Jul 05 2001