A091630 Numbers n + product of digits associated with A091628.

29, 235, 2247, 22271, 222319, 2222415, 22222607, 222222991, 2222223759, 22222225295, 222222228367, 2222222234511, 22222222246799, 222222222271375, 2222222222320527, 22222222222418831, 222222222222615439

Offset: 1

Author

Enoch Haga, Jan 24 2004

Keywords

• base
• easy
• nonn

Comments

Sequence arising in Farideh Firoozbakht's solution to Prime Puzzle 251 - 23 is the only pointer prime (A089823) not containing the digit "1".

The monotonically increasing value of successive product of digits (A091629) strongly suggests that in successive n the digit 1 must be present.

Examples

			a(1) = 23 + 6 = 29.
		

Links

• Carlos Rivera's Prime Puzzles and Problems Connection, Puzzle 251, Pointer primes
• Index entries for linear recurrences with constant coefficients, signature (13,-32,20).

Crossrefs

Cf. A089823, A091628, A091629, A091631, A091632.

Formula

a(n) = A091628(n) + A091629(n).

From Chai Wah Wu, Feb 12 2021: (Start)

a(n) = 13*a(n-1) - 32*a(n-2) + 20*a(n-3) for n > 3.

G.f.: x*(-120*x^2 + 142*x - 29)/((x - 1)*(2*x - 1)*(10*x - 1)). (End)

Extensions

Edited and extended by Ray Chandler, Feb 07 2004