A085718 Numbers n such that sopfr(n)/spf(n) is a semiprime and sopfr(n)/lpf(n) is a semiprime, where sopfr(n) = A001414(n) is sum of primes dividing n (with repetition), spf(n) and lpf(n) are smallest and largest primes dividing n, respectively. Also, spf(n)!=lpf(n).

72, 576, 648, 750, 800, 900, 960, 1080, 3430, 4116, 4900, 5880, 6272, 7000, 7056, 7938, 8400, 8960, 9450, 10080, 10752, 11340, 12096, 13608, 18750, 20000, 22500, 24000, 25600, 27000, 28800, 30375, 30720, 32400, 34560, 36450, 36864, 37268

Offset

1,1

Links

Table of n, a(n) for n=1..38.

Example

648=2^3*3^4 is a term because 2+2+2+3+3+3+3 = 18 and 18/2 = 9 and 18/3 = 6.

Crossrefs

Sequence in context: A353218 A204484 A235178 * A205329 A077120 A200451

Adjacent sequences: A085715 A085716 A085717 * A085719 A085720 A085721

Keyword

nonn

Author

Jason Earls, Jul 19 2003

Status

approved