A062532 -id:A062532 - cp's OEIS frontend

A226025 Odd composite numbers that are not squares of primes.

15, 21, 27, 33, 35, 39, 45, 51, 55, 57, 63, 65, 69, 75, 77, 81, 85, 87, 91, 93, 95, 99, 105, 111, 115, 117, 119, 123, 125, 129, 133, 135, 141, 143, 145, 147, 153, 155, 159, 161, 165, 171, 175, 177, 183, 185, 187, 189, 195, 201, 203, 205, 207, 209, 213, 215, 217

Offset: 1

Arkadiusz Wesolowski, Jun 07 2013

nonn

Numbers that are in A071904 (odd composite numbers) but not in A001248 (squares of primes).
First differs from its subsequence A082686 in a(16)=81 which is not in A082686. More precisely, A226025 \ A082686 = A062532 \ {1} = A014076^2 \ {1}. - M. F. Hasler, Oct 20 2013
Odd numbers that are greater than the square of their least prime factor - Odimar Fabeny, Sep 08 2014

Arkadiusz Wesolowski, Table of n, a(n) for n = 1..10000

Subsequence of A071904. Cf. A226603.

a226025 n = a226025_list !! (n-1)
a226025_list = filter ((/= 2) . a100995) a071904_list
-- Reinhard Zumkeller, Jun 15 2013

[n: n in [3..217 by 2] | not IsPrime(n) and not IsSquare(n) or IsSquare(n) and not IsPrime(Floor(n^(1/2)))];

select(n -> not(isprime(n)) and (not(issqr(n)) or not(isprime(sqrt(n)))), [seq(2*i+1,i=1..1000)]); # Robert Israel, Sep 08 2014

Select[Range[3, 217, 2], ! PrimeQ[#] && ! PrimeQ@Sqrt[#] &]
r = Prime@Range[2, 6]^2; Complement[Select[Range[3, Last[r] - 2, 2], ! PrimeQ[#] &], Most[r]]
Select[Range[3,251,2],NoneTrue[{#,Sqrt[#]},PrimeQ]&] (* Harvey P. Dale, Sep 06 2021 *)

is_A226025(n)={bittest(n,0)&&!isprime(n,0)&&!(issquare(n)&&isprime(sqrtint(n)))&&n>1} \\ - M. F. Hasler, Oct 20 2013

A226025 = { odd x>1 | A100995(x) = 0 or A100995(x) > 2 }. - M. F. Hasler, Oct 20 2013

A253261 Odd Brazilian squares.

Original entry on oeis.org

81, 121, 225, 441, 625, 729, 1089, 1225, 1521, 2025, 2401, 2601, 3025, 3249, 3969, 4225, 4761, 5625, 5929, 6561, 7225, 7569, 8281, 8649, 9025, 9801, 11025, 12321, 13225, 13689, 14161, 14641, 15129, 15625, 16641, 17689, 18225, 19881, 20449, 21025, 21609, 23409, 24025, 25281, 25921, 27225, 28561

Offset: 1

Derek Orr, Apr 30 2015

121 is believed to be the only number of the form p^2 for prime p.

The previous comment conjectures the 1 and the 121 are the only difference with respect to A062532. - R. J. Mathar, Jul 25 2015

Cf. A125134, A257521.

for(n=4, 10^5, for(b=2, n-2, d=digits(n, b); if(vecmin(d)==vecmax(d)&&(n+1)%2==0&&issquare(n), print1(n, ", "); break)))

cp's OEIS Frontend

A226025 Odd composite numbers that are not squares of primes.

Views

Author

Keywords

Comments

Links

Crossrefs

Programs

Haskell

Magma

Maple

Mathematica

PARI

Formula