A144158 (1=1, 2=2, 3=3, 4=2^2, 5=5, 6=2*3, 7=7, 8=2^3, 9=3^2, 10=2*5, 11=11, 12=2^2*3, 13=13, ...) becomes (1*1*2, 2*3*3, 4*2*2, 5*5*6, 2*3*7, 7*8*2, 3*9*3, 2*10*2, 5*11*11, 12*2*2, 3*13*13, ...).

2, 18, 16, 150, 42, 112, 81, 40, 605, 48, 507, 196, 225, 128, 5202, 12, 7220, 20, 441, 484, 12696, 18, 250, 676, 243, 112, 5887, 180, 4805, 320, 1089, 1156, 1225, 144, 222, 2812, 2223, 1040, 615, 3444, 903, 3784, 990, 30, 2116, 106032, 24, 686, 500, 306

Offset: 1

Author

Juri-Stepan Gerasimov, Nov 17 2008

Keywords

• nonn

Examples

			3*13*13 = 507 = a(11),
14*2*7 = 196 = a(12),
15*3*5 = 225 = a(13),
16*2*4 = 128 = a(14),
17*17*18 = 5202 = a(15),
2*3*2 = 12 = a(16),
19*19*20 = 7220 = a(17),
etc.
		

Crossrefs

Cf. A141186, A136740, A136811, A143717.

Programs

Maple

pflat := proc(nmax) local a, ifs, n, p, c ; a := [1,1] ; for n from 2 to nmax do a := [op(a),n] ; ifs := ifactors(n)[2] ; for p in ifs do a := [op(a),op(1,p)] ; if op(2,p) > 1 then a := [op(a),op(2,p)] ; fi; od: od: a ; end: L := pflat(300) ; for n from 1 to nops(L)-3 by 3 do printf("%d,", op(n,L)*op(n+1,L)*op(n+2,L) ) ; end do: # R. J. Mathar, Apr 29 2010

Extensions

a(37) and terms after a(46) corrected by R. J. Mathar, Apr 29 2010