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A073946 Squares k such that k + pi(k) is a prime. 3
9, 36, 81, 121, 361, 625, 961, 3136, 6724, 8281, 9604, 10609, 12996, 13225, 19881, 25281, 38025, 39204, 40000, 43264, 44944, 45796, 47961, 60516, 64009, 79524, 80089, 80656, 83521, 86436, 90000, 93636, 103684, 117649, 121801, 129600 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Robert Israel, Table of n, a(n) for n = 1..1000

EXAMPLE

a(1)=9, since 9 is a square, pi(9)=4 and 9+4=13 is a prime.

MAPLE

select(t -> isprime(t + numtheory:-pi(t)), [seq(i^2, i=1..1000)]); # Robert Israel, Mar 21 2017

MATHEMATICA

Select[Range[1000]^2, PrimeQ[# + PrimePi[#]] &] (* Indranil Ghosh, Mar 21 2017 *)

PROG

(PARI)

v=vector(1000);

for(n=1, 1000, v[n] = n^2);

for(n=1, 1000, if(isprime(v[n] + primepi(v[n])), print1(v[n], ", "))) \\ Indranil Ghosh, Mar 21 2017

(Python)

from sympy import primepi, isprime

N = [x**2 for x in xrange(1, 1001)]

print [n for n in N if isprime(n + primepi(n))] # Indranil Ghosh, Mar 21 2017

CROSSREFS

This sequence is a subsequence of sequence A077510. The corresponding sequence of primes is A113943 and the square roots of the original sequence is A113944.

Sequence in context: A068810 A077115 A297584 * A016766 A242538 A083353

Adjacent sequences:  A073943 A073944 A073945 * A073947 A073948 A073949

KEYWORD

nonn

AUTHOR

David Garber, Nov 13 2002

STATUS

approved

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Last modified December 6 16:24 EST 2019. Contains 329808 sequences. (Running on oeis4.)