A346138 Sphenic numbers that are the product of Mersenne primes.

651, 2667, 11811, 27559, 172011, 761763, 1777447, 2752491, 3120771, 7281799, 11010027, 12189603, 28442407, 32247967, 48758691, 49938051, 113770279, 116522119, 199753347, 466091143, 516026527, 2064117919, 3220807683, 7515217927, 12883304451, 30061043719, 33281679391, 45097156587, 133127479327

Offset: 1

Author

Timothy L. Tiffin, Jul 06 2021

Keywords

• nonn

Comments

The largest known sphenic number is a term of this sequence.

a(n) == 3 (mod 4) for n >= 1.

Examples

			a(1) = 651, since 651 = 3*7*31.
a(2) = 2667, since 2667 = 3*7*127.
a(3) = 11811, since 11811 = 3*31*127.
		

Links

• Wikipedia, Sphenic number (lists the largest known sphenic number)
• Wikipedia, Mersenne prime
• Index to sequences related to prime signature

Crossrefs

Cf. A007304, A046528, A144856.

Programs

Mathematica

M = 2^MersennePrimeExponent[Range[12]] - 1; Take[ Union[ Times @@@ Subsets[ M, {3}]], 50]