A364875 The slowest increasing sequence of triprimes with alternating parity.

8, 27, 28, 45, 50, 63, 66, 75, 76, 99, 102, 105, 110, 117, 124, 125, 130, 147, 148, 153, 154, 165, 170, 171, 172, 175, 182, 195, 212, 231, 236, 245, 246, 255, 258, 261, 266, 273, 282, 285, 286, 325, 332, 333, 338, 343, 354, 357, 366, 369, 370, 385, 388, 399, 402, 423, 426, 429, 430, 435, 436, 455

Offset

1,1

Comments

a(n) is the least triprime (i.e., product of exactly 3 primes, not necessarily distinct) > a(n-1) such that (a(n) mod 2) != (a(n-1) mod 2).

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Example

a(1) is the first triprime, 8 = 2^3, which is even.
a(2) is the next odd triprime, which is 27 = 3^3.
a(3) is the next even triprime, which is 28 = 2^2 * 7.

Maple

R:= 8: x:= 7: count:= 1:
while count < 100 do
   x:= x+2;
   if numtheory:-bigomega(x) = 3 then
      count:= count+1; R:= R, x; x:= x-1
   fi
od:
R;

Mathematica

s = {8}; m = 8; Do[n = m + 1; While[3 != PrimeOmega[n], n = n +
2]; AppendTo[s, m = n], {199}]; s

Crossrefs

Cf. A014612, A254923.

Sequence in context: A077107 A335018 A070498 * A358240 A084698 A070497

Adjacent sequences: A364872 A364873 A364874 * A364876 A364877 A364878

Keyword

nonn

Author

Zak Seidov and Robert Israel, Aug 11 2023

Status

approved