A363167 Products of four distinct strong primes.

200651, 222343, 283679, 319957, 363341, 385033, 408221, 428417, 452353, 463573, 483923, 491249, 513689, 526031, 544357, 546601, 547723, 580261, 605693, 671143, 688721, 696377, 698819, 739211, 740333, 742951, 743699, 747881, 771661, 774367, 783343, 790801, 808027, 820369

Offset

1,1

Comments

Strong primes: prime(n) > (prime(n-1) + prime(n+1))/2.

Links

Table of n, a(n) for n=1..34.

Example

200651 = 11*17*29*37 and 11 > (7+13)/2, 17 > (13+19)/2, 29 > (23+31)/2, 37 > (31+41)/2.
222343 = 11*17*29*41 and 11 > (7+13)/2, 17 > (13+19)/2, 29 > (23+31)/2, 41 > (37+43)/2.
283679 = 11*17*37*41 and 11 > (7+13)/2, 17 > (13+19)/2, 37 > (31+41)/2, 41 > (37+43)/2.

Mathematica

strongQ[p_] := p > 2 && 2*p > Total[NextPrime[p, {-1, 1}]]; Select[Range[1, 10^6, 2], (f = FactorInteger[#])[[;; , 2]] == {1, 1, 1, 1} && AllTrue[f[[;; , 1]], strongQ] &] (* Amiram Eldar, Sep 08 2023 *)

Crossrefs

Cf. A046386, A051634, A364778, A363782.

Sequence in context: A345637 A346350 A345661 * A179224 A237374 A202316

Adjacent sequences: A363164 A363165 A363166 * A363168 A363169 A363170

Keyword

nonn

Author

Massimo Kofler, Sep 07 2023

Status

approved