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A264887 Numbers in A007504 such that omega(a(n)) = Omega(a(n)) = 4. 2
5830, 6870, 13490, 16401, 58406, 60146, 61910, 65534, 75130, 136114, 148827, 153178, 213538, 257358, 269074, 273054, 327198, 354102, 377310, 382038, 403611, 443685, 475323, 488774, 496905, 665130, 684510, 691026, 799846, 817563 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Omega and omega are given in A001221 and A001222, respectively.

The corresponding numbers of prime summands, k(n), are 53, 57, 77, 84, 149, 151, 153, 157, 167, 219, 228, 231, 269, 293, 299, 301, 327, 339, 349, 351, 360, 376, 388, 393, 396, 453, 459, 461, 493, 498, ...

Intersection of A007504 and A046386 (products of four distinct primes). - Michel Marcus, Dec 15 2015

LINKS

John Cerkan, Table of n, a(n) for n = 1..10000

EXAMPLE

For n = 1, k(n) = 53 and a(n) = A007504(53) = 5830 = 2*5*11*53.

For n = 2, k(n) = 57 and a(n) = A007504(57) = 6870 = 2*3*5*229.

For n = 3, k(n) = 77 and a(n) = A007504(77) = 13490 = 2*5*19*71.

For n = 4, k(n) = 84 and a(n) = A007504(84) = 16401 = 3*7*11*71.

For n = 5, k(n) = 149 and a(n) = A007504(149) = 58406 = 2*19*29*53.

For n = 6, k(n) = 151 and a(n) = A007504(151) = 60146 = 2*17*29*61.

Note that for each of the elements of the sequence, omega(a(n)) = Omega(a(n)) = 4, i.e., the number of prime factors of a(n) = the number of distinct prime factors of a(n) = 4.

MATHEMATICA

t = Accumulate@ Prime@ Range@ 600; Select[t, PrimeNu@ # == PrimeOmega@ # == 4 &] (* Michael De Vlieger, Nov 27 2015, after Zak Seidov at A007504 *)

PROG

(PARI) lista(nn) = {my(s = 0); for (n=1, nn, s += prime(n); if ((omega(s) == 4) && (bigomega(s)==4), print1(s, ", ")); ); } \\ Michel Marcus, Nov 28 2015

CROSSREFS

Cf. A001221, A001222, A007504, A013918, A046386, A189072, A264885.

Sequence in context: A131494 A234804 A261941 * A035903 A251189 A269185

Adjacent sequences:  A264884 A264885 A264886 * A264888 A264889 A264890

KEYWORD

nonn

AUTHOR

Debapriyay Mukhopadhyay, Nov 27 2015

STATUS

approved

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Last modified May 16 19:46 EDT 2021. Contains 343951 sequences. (Running on oeis4.)