A076207 Triangular numbers whose sum of primes from smallest to largest prime factor is triangular and whose sum of composites from smallest to largest prime factor is triangular.

3, 21, 105, 325, 7875, 9568125

Offset: 1

Author

Jason Earls, Nov 02 2002

Keywords

• more
• nonn

Comments

No more terms < 2.77*10^12. - David Wasserman, Jul 20 2005

a(7) > 2*10^15. - Donovan Johnson, Feb 03 2013

Examples

			325 = 5^2*13, sum of primes between: 5+7+11+13 = 36, triangular; sum of composites between: 6+8+9+10+12 = 45, triangular.
		

Crossrefs

Cf. A000217, A074036, A074037.

Extensions

Offset corrected by Donovan Johnson, Feb 03 2013