A368697 Numbers that are divisible by the squares of two distinct primes and whose arithmetic derivative (A003415) is a squarefree number of the form 4k+2.

11025, 17325, 27225, 28665, 29925, 36225, 37485, 38025, 40425, 47025, 48825, 49725, 53361, 56925, 63525, 63945, 65025, 69825, 70785, 74025, 74529, 76725, 81225, 81585, 84525, 84825, 88725, 90405, 92169, 92565, 92925, 98325, 105525, 106425, 108225, 110925, 111573, 111825, 113925, 116325, 116865, 117117, 119025, 119925

Offset: 1

Author

Antti Karttunen, Jan 09 2024

Keywords

• nonn

Crossrefs

Intersection of A036785 and A368696, i.e., of A036785, A327862 and A328393.

Cf. A003415, A057521.

Programs

PARI

A003415(n) = if(n<=1, 0, my(f=factor(n)); n*sum(i=1, #f~, f[i, 2]/f[i, 1]));
A057521(n) = { my(f=factor(n)); prod(i=1, #f~, if(f[i, 2]>1, f[i, 1]^f[i, 2], 1)); };
isA368697(n) = if(omega(A057521(n))<2, 0, my(d=A003415(n)); ((2==(d%4))&&issquarefree(d)));