A137507 - OEIS

A137507

a(n) = 100^[n/10] + 2*n*10^[n/10]: inspired by Engel expansion of Pi.

1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 300, 320, 340, 360, 380, 400, 420, 440, 460, 480, 14000, 14200, 14400, 14600, 14800, 15000, 15200, 15400, 15600, 15800, 1060000, 1062000, 1064000, 1066000, 1068000, 1070000, 1072000, 1074000, 1076000, 1078000, 100800000, 100820000

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,2

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (0,0,0,0,0,0,0,0,0,120,0,0,0,0,0,0,0,0,0,-2100,0,0,0,0,0,0,0,0,0,10000).

MATHEMATICA

Table[100^(Floor[n/10]) + 2*n*10^(Floor[n/10]), {n, 0, 50}] (* G. C. Greubel, Feb 23 2017 *)

PROG

(PARI) a(n) = (n + 10^(floor(n/10)))^2 - n^2;

(PARI) vector(30, n, n--; 2*n*10^(n\10) + 100^(n\10)) \\ M. F. Hasler, May 02 2008

(SageMath) [(n + 10^(floor(n/10)))^2 - n^2 for n in range(0, 42)] # Stefano Spezia, Apr 16 2025

CROSSREFS

Cf. A006784.

Sequence in context: A352547 A014261 A066640 * A061808 A248608 A362680

Adjacent sequences: A137504 A137505 A137506 * A137508 A137509 A137510

KEYWORD

nonn,easy

AUTHOR

Alexander R. Povolotsky, Apr 23 2008

EXTENSIONS

Edited by M. F. Hasler and N. J. A. Sloane, May 02 2008

STATUS

approved