A268733 a(n) = A000203(A251720(n)).

28, 78, 248, 684, 1862, 3294, 6140, 9144, 16590, 27872, 37734, 59094, 75812, 90864, 121878, 171780, 219542, 257244, 328104, 378362, 432240, 530964, 627570, 785078, 969714, 1071512, 1157004, 1271270, 1366974, 1649024, 2145924

Offset: 1

Author

Zak Seidov, Feb 12 2016

Keywords

• nonn

Comments

Let p=prime(n)=A000040(n) and q=prime(n+1)=A000040(n+1) then a(n)=sigma(p^2*q)=1+p+q+p^2+ p*q+p^2*q.

Crossrefs

Cf. A000040, A000203, A251720.

Programs

Mathematica

p=1; Table[p=NextPrime[p];q=NextPrime[p];1+p+q+p^2+p*q+p^2*q,{20}]

PARI

p=1;for(n=1,20,p=nextprime(p+1);q=nextprime(p+1);print1(sigma(p^2*q)","))