A100412 a(n) = 8*10^n - 7.

1, 73, 793, 7993, 79993, 799993, 7999993, 79999993, 799999993, 7999999993, 79999999993, 799999999993, 7999999999993, 79999999999993, 799999999999993, 7999999999999993, 79999999999999993, 799999999999999993

Offset

0,2

Comments

Also: Numbers n such that n is reversal(n)-th odd number. (This was the original definition. - Ed.)

All semiprimes in this sequence (n = 2, 4, 7, 9, 11, 16, 18, 23, 31, 32, 40, ...) are in A136543. - M. F. Hasler, Nov 03 2012

Links

G. C. Greubel, Table of n, a(n) for n = 0..500

Index entries for linear recurrences with constant coefficients, signature (11,-10).

Formula

From Colin Barker, Oct 14 2014: (Start)

a(n) = 10*a(n-1) + a(n-2) - 10*a(n-3).

G.f.: (1+62*x)/((1-x)*(1-10*x)). (End)

E.g.f.: 8*exp(10*x) - 7*exp(x). - G. C. Greubel, Apr 14 2023

Example

793 is in the sequence because 793 is 397th odd number.
1 is in the sequence because 1 is the 1st odd number. - M. F. Hasler, Nov 03 2012

Mathematica

Table[8*10^n-7, {n, 0, 20}]

Prog

(Maxima) A100412(n):=8*10^n-7$
makelist(A100412(n), n, 0, 17); /* Martin Ettl, Nov 08 2012 */
(PARI) Vec((1+62*x)/((1-x)*(1-10*x)) + O(x^100)) \\ Colin Barker, Oct 14 2014
(Magma) [8*10^n -7: n in [0..20]]; // G. C. Greubel, Apr 14 2023
(SageMath) [8*10^n -7 for n in range(21)] # G. C. Greubel, Apr 14 2023

Crossrefs

Cf. A100413, A136543.

Sequences of the form m*10^n - 7: 3*A033175 (m=1, 10), A086943 (m=3), 3*A185127 (m=4), A086578 (m=7), this sequence (m=8).

Sequence in context: A063784 A066101 A272768 * A169830 A197341 A104907

Adjacent sequences: A100409 A100410 A100411 * A100413 A100414 A100415

Keyword

base,easy,nonn

Author

Farideh Firoozbakht, Dec 08 2004

Extensions

Edited and extended to offset 0 by M. F. Hasler, Nov 03 2012

Status

approved