A362410 Numbers k such that A000292(k) is in A046386.
19, 33, 45, 51, 59, 61, 65, 67, 69, 77, 85, 93, 105, 109, 113, 129, 141, 165, 181, 193, 197, 201, 211, 213, 217, 221, 227, 237, 257, 261, 267, 277, 291, 301, 309, 317, 345, 347, 353, 357, 365, 393, 397, 401, 409, 417, 421, 437, 445, 461, 465, 477, 497, 521, 561, 569, 597, 613, 633, 653, 661, 677
Offset: 1
Keywords
Examples
a(3) = 45 is a term because 45*46*47/6 = 16215 = 3*5*23*47 is the product of four distinct primes.
Links
- Robert Israel, Table of n, a(n) for n = 1..10000
Programs
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Maple
filter:= k -> ifactors(k*(k+1)*(k+2)/6)[2][..,2] = [1,1,1,1]; select(filter, [seq(i,i=1..1000,2)]);
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Mathematica
p4dpQ[n_]:=With[{c=(n(n+1)(n+2))/6},PrimeNu[c]==PrimeOmega[c]==4]; Select[Range[ 700],p4dpQ] (* Harvey P. Dale, May 06 2024 *) -
PARI
isok(k) = my(t=k*(k+1)*(k+2)/6); (omega(t)==4) && (bigomega(t)==4); \\ Michel Marcus, Apr 20 2023
Comments