A073946 Squares k such that k + pi(k) is a prime.
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
Offset: 1
Keywords
Examples
a(1)=9, since 9 is a square, pi(9)=4 and 9+4=13 is a prime.
Links
- Robert Israel, Table of n, a(n) for n = 1..1000
Crossrefs
Programs
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Maple
select(t -> isprime(t + numtheory:-pi(t)), [seq(i^2,i=1..1000)]); # Robert Israel, Mar 21 2017
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Mathematica
Select[Range[1000]^2, PrimeQ[# + PrimePi[#]] &] (* Indranil Ghosh, Mar 21 2017 *)
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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
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Python
from sympy import primepi, isprime N = (x**2 for x in range(1, 1001)) print([n for n in N if isprime(n + primepi(n))]) # Indranil Ghosh, Mar 21 2017