A116453 Third smallest number with exactly n prime factors.

5, 9, 18, 36, 72, 144, 288, 576, 1152, 2304, 4608, 9216, 18432, 36864, 73728, 147456, 294912, 589824, 1179648, 2359296, 4718592, 9437184, 18874368, 37748736, 75497472, 150994944, 301989888, 603979776, 1207959552, 2415919104

Offset

1,1

Comments

Smallest term in A116451 having exactly n prime factors;

a(n) = A116451(A116454(n)) = A116454(n) + 2 * n + 3;

a(n) = A005010(n-2) for n > 1.

Links

Table of n, a(n) for n=1..30.

Example

a(1) =  5 = A000040(3) > A000040(2) =  3 > A000040(1) =  2;
a(2) =  9 = A001358(3) > A001358(2) =  6 > A001358(1) =  4;
a(3) = 18 = A014612(3) > A014612(2) = 12 > A014612(1) =  8;
a(4) = 36 = A014613(3) > A014613(2) = 24 > A014613(1) = 16.

Prog

(Python)
def A116453(n): return 9<<n-2 if n>1 else 5 # Chai Wah Wu, Aug 23 2024

Crossrefs

Sequence in context: A110349 A036832 A257595 * A046578 A046590 A372997

Adjacent sequences: A116450 A116451 A116452 * A116454 A116455 A116456

Keyword

nonn

Author

Reinhard Zumkeller, Feb 16 2006

Status

approved