A358818 a(n) is the least number k such that A046660(k) = A046660(k+1) = n.

1, 44, 135, 80, 8991, 29888, 123200, 2316032, 1043199, 24151040, 217713663, 689278976, 11573190656, 76876660736, 311969153024, 2035980763136, 2741258240000, 215189482110975

Offset: 0

Author

Amiram Eldar, Dec 02 2022

Keywords

• nonn
• more

Comments

a(14) <= 314944159743.

a(18) > 10^14.5; a(19) = 275892612890624; a(20) > 10^14.5. - Martin Ehrenstein, Dec 11 2022

Crossrefs

Cf. A046660.

Subsequence of A358817.

Similar sequences: A052215, A059737, A093548, A115186.

Programs

Mathematica

e[n_] := PrimeOmega[n] - PrimeNu[n]; a[n_] := Module[{k = 1}, While[e[k] != n || e[k + 1] != n, k++]; k]; Array[a, 10, 0]

PARI

e(n) = {my(f = factor(n)); bigomega(f) - omega(f)};
a(n) = {my(k=1); while(e(k) != n || e(k+1) !=n , k++); k};

Extensions

a(14)-a(16) from Martin Ehrenstein, Dec 04 2022

a(17) from Martin Ehrenstein, Dec 09 2022