A091630 - OEIS

%I #12 Feb 12 2021 18:16:15

%S 29,235,2247,22271,222319,2222415,22222607,222222991,2222223759,

%T 22222225295,222222228367,2222222234511,22222222246799,

%U 222222222271375,2222222222320527,22222222222418831,222222222222615439

%N Numbers n + product of digits associated with A091628.

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

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

%H Carlos Rivera's Prime Puzzles and Problems Connection, <a href="http://www.primepuzzles.net/puzzles/puzz_251.htm">Puzzle 251, Pointer primes</a>

%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (13,-32,20).

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

%F From _Chai Wah Wu_, Feb 12 2021: (Start)

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

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

%e a(1) = 23 + 6 = 29.

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

%K base,easy,nonn

%O 1,1

%A _Enoch Haga_, Jan 24 2004

%E Edited and extended by _Ray Chandler_, Feb 07 2004