A355332 Numbers k such that k | A020696(k) and (k+1) | A020696(k+1).

1, 201824, 227799, 313599, 395199, 544824, 638000, 654975, 799799, 862784, 1056159, 1204280, 1269729, 1447550, 1890944, 2276351, 2460975, 2481115, 2781999, 2821272, 3348224, 3382379, 3403700, 3832191, 3864575, 3956120, 5142500, 5961950, 6116175, 6401024, 7050120

Offset

1,2

Comments

Numbers k such that k and k+1 are both in A355331.

Are there 3 consecutive integers in A355331?

There are no such 3 consecutive integers below 10^10. - Amiram Eldar, Oct 12 2023

Links

Amiram Eldar, Table of n, a(n) for n = 1..2000

Example

1 is a term since A020696(1) = 2 is divisible by 1 and A020696(2) = 6 is divisible 2.

Mathematica

q[n_] := Divisible[Times @@ (Divisors[n] + 1), n]; Select[Range[10^6], q[#] && q[#+1] &]

Prog

(PARI) f(n) = my(d = divisors(n)); prod(i=1, #d, d[i]+1); \\ A020696
isok(k) = !(f(k) % k) && !(f(k+1) % (k+1)); \\ Michel Marcus, Jun 30 2022

Crossrefs

Cf. A020696, A355331.

Sequence in context: A233838 A233837 A252498 * A274815 A242518 A235929

Adjacent sequences: A355329 A355330 A355331 * A355333 A355334 A355335

Keyword

nonn

Author

Amiram Eldar, Jun 29 2022

Status

approved