Compound filter: a(n) = P(sigma(n), sigma(2n)), where P(n,k) is sequence A000027 used as a pairing function, and sigma is the sum of divisors (A000203).

A286359

Compound filter: a(n) = P(sigma(n), sigma(2n)), where P(n,k) is sequence A000027 used as a pairing function, and sigma is the sum of divisors (A000203).

Terms

    a(0) =4a(1) =39a(2) =109a(3) =217a(4) =259a(5) =753a(6) =473a(7) =1005a(8) =1288a(9) =1729a(10) =1093a(11) =3769a(12) =1499a(13) =3105a(14) =4489a(15) =4309a(16) =2503a(17) =8295a(18) =3101a(19) =8557a(20) =8033a(21) =7057a(22) =4489a(23) =16713a(24) =7534a(25) =9633a(26) =12601a(27) =15281a(28) =7051a(29) =28513

External references