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

1,1

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.

Links

Table of n, a(n) for n=1..17.

Carlos Rivera's Prime Puzzles and Problems Connection, Puzzle 251, Pointer primes

Index entries for linear recurrences with constant coefficients, signature (13,-32,20).

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)

Example

a(1) = 23 + 6 = 29.

Crossrefs

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

Sequence in context: A228408 A042636 A372962 * A251424 A027112 A142095

Adjacent sequences: A091627 A091628 A091629 * A091631 A091632 A091633

Keyword

base,easy,nonn

Author

Enoch Haga, Jan 24 2004

Extensions

Edited and extended by Ray Chandler, Feb 07 2004

Status

approved