A362435 a(1) = 18; thereafter a(n) = a(n-1) + abs(difference between first two digits of a(n-1)).

18, 25, 28, 34, 35, 37, 41, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44

Offset

1,1

Comments

44 is a fixed point.

References

GCHQ, The GCHQ Puzzle Book, Penguin, 2016. See page 36.

Links

Table of n, a(n) for n=1..66.

Index entries for linear recurrences with constant coefficients, signature (1).

Formula

G.f.: x*(18 + 7*x + 3*x^2 + 6*x^3 + x^4 + 2*x^5 + 4*x^6 + 3*x^7)/(1 - x). - Elmo R. Oliveira, Aug 03 2024

Mathematica

NestList[# + Abs[Subtract @@ IntegerDigits[#][[;; 2]]] &, 18, 64] (* or *)
PadRight[{18, 25, 28, 34, 35, 37, 41}, 65, 44] (* Paolo Xausa, Jan 22 2026 *)

Crossrefs

Cf. A006507, A232485.

Sequence in context: A003300 A245022 A393026 * A248111 A109769 A350773

Adjacent sequences: A362432 A362433 A362434 * A362436 A362437 A362438

Keyword

nonn,easy

Author

N. J. A. Sloane, Apr 21 2023

Status

approved