A178509 Smallest value of k for which 6*k+1 divides the subset of centered hexagonal terms included in A177019 that admit only factors like 6*k+1.

1, 55, 26, 5, 50005000, 1, 1, 16, 1936, 500000000500000000, 15333927, 1, 1, 18316, 3, 7, 1526, 1, 1, 12, 73, 38, 47, 1, 1, 121, 43502, 12, 11, 1, 1, 18, 3, 5, 10, 1, 1, 481, 2043419605725853, 921, 3835, 1, 1, 12, 10, 13, 25, 1, 1, 18, 3, 12, 62, 1, 1, 76, 398, 7

Offset: 0

Author

Giacomo Fecondo, May 29 2010, May 30 2010

Keywords

• nonn

Comments

The terms a(0), a(1), a(4) and a(9) confirm the primality of the terms included in A160432;

k assumes the value 1 when the value of n in a(n) is equal to 6*i or 6*i-1 where i is a positive integer.

Examples

			a(0)= 1 so 6*1+1 = 7 is the minimum factor dividing 7; a(1)= 55 so 6*55+1 = 331 the minimum factor dividing 331; a(2)= 26 so 6*26+1 = 157 the minimum factor dividing 30301; a(3)= 5 so 6*5+1 = 31 the minimum factor dividing 3003001; a(10)=15333927 so 6*15333927+1 = 92003563 the minimum factor dividing 3*10^20+3*10^10+1.
		

Crossrefs

Cf. A177019, A160432.