This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A303555 Triangle read by rows: T(n,k) = 2^(n-k)*prime(k)#, 1 <= k <= n, where prime(k)# is the product of first k primes. 9
 2, 4, 6, 8, 12, 30, 16, 24, 60, 210, 32, 48, 120, 420, 2310, 64, 96, 240, 840, 4620, 30030, 128, 192, 480, 1680, 9240, 60060, 510510, 256, 384, 960, 3360, 18480, 120120, 1021020, 9699690, 512, 768, 1920, 6720, 36960, 240240, 2042040, 19399380, 223092870, 1024, 1536, 3840, 13440, 73920, 480480, 4084080, 38798760, 446185740, 6469693230 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS T(n,k) = the smallest number m having exactly n prime divisors counted with multiplicity and exactly k distinct prime divisors. LINKS Eric Weisstein's World of Mathematics, Prime Factor Eric Weisstein's World of Mathematics, Distinct Prime Factors Eric Weisstein's World of Mathematics, Primorial EXAMPLE T(5,4) = 420 = 2^2*3*5*7, hence 420 is the smallest number m such that bigomega(m) = 5 and omega(m) = 4 (see A189982). Triangle begins:     2;     4,   6;     8,  12,  30;    16,  24,  60,  210;    32,  48, 120,  420, 2310;    64,  96, 240,  840, 4620, 30030;   128, 192, 480, 1680, 9240, 60060, 510510;   ... MATHEMATICA Flatten[Table[2^(n - k) Product[Prime[j], {j, k}], {n, 10}, {k, n}]] CROSSREFS Cf. A000079, A001221, A001222, A002110, A005179, A038547, A055079, A070175, A303557 (central terms). Sequence in context: A036035 A063008 A059901 * A136101 A187779 A086141 Adjacent sequences:  A303552 A303553 A303554 * A303556 A303557 A303558 KEYWORD nonn,tabl AUTHOR Ilya Gutkovskiy, Apr 26 2018 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified September 17 04:58 EDT 2019. Contains 327119 sequences. (Running on oeis4.)