

A172409


Numbers n such that neither n2 nor n3 is prime.


0



0, 1, 2, 3, 11, 12, 17, 18, 23, 24, 27, 28, 29, 30, 35, 36, 37, 38, 41, 42, 47, 48, 51, 52, 53, 54, 57, 58, 59, 60, 65, 66, 67, 68, 71, 72, 77, 78, 79, 80, 83, 84, 87, 88, 89, 90, 93, 94, 95, 96, 97, 98, 101, 102, 107, 108, 113, 114, 117, 118, 119, 120, 121, 122, 123, 124
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OFFSET

1,3


LINKS

Table of n, a(n) for n=1..66.


FORMULA

a(n) ~ n.  Charles R Greathouse IV, Jun 13 2017


EXAMPLE

a(1)=0 because 02=2 and 03=1 are nonprime.


MATHEMATICA

Join[{0, 1}, Select[Range[150], !PrimeQ[#2]&&!PrimeQ[#3]&]] (* 0 and 1 are in the sequence because primes are usually defined to include only positive integers, but because Mathematica treats many negative numbers, including 2 and 3, as primes, it is necessary to include 0 and 1 via "Join". *) (* Harvey P. Dale, Aug 06 2012 *)


PROG

(PARI) is(n)=!isprime(n2) && !isprime(n3) \\ Charles R Greathouse IV, Jun 13 2017


CROSSREFS

Sequence in context: A116029 A060812 A212129 * A062936 A136972 A227764
Adjacent sequences: A172406 A172407 A172408 * A172410 A172411 A172412


KEYWORD

nonn,easy,less


AUTHOR

JuriStepan Gerasimov, Feb 06 2010


EXTENSIONS

Corrected by Charles R Greathouse IV, Mar 25 2010


STATUS

approved



