A100413 -id:A100413 - cp's OEIS frontend

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

Farideh Firoozbakht, Dec 08 2004

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

			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

G. C. Greubel, Table of n, a(n) for n = 0..500
Index entries for linear recurrences with constant coefficients, signature (11,-10).

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).

[8*10^n -7: n in [0..20]]; // G. C. Greubel, Apr 14 2023

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

A100412(n):=8*10^n-7$
makelist(A100412(n),n,0,17); /* Martin Ettl, Nov 08 2012 */

Vec((1+62*x)/((1-x)*(1-10*x)) + O(x^100)) \\ Colin Barker, Oct 14 2014

[8*10^n -7 for n in range(21)] # G. C. Greubel, Apr 14 2023

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

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

A100414 Numbers n such that n is R(n)-th composite number where R(n) is the digit reversal of n (A002808(A004086(n))=n).

Original entry on oeis.org

21, 48034, 69926, 180461, 214591, 409473, 563715, 41630193, 253385633342, 661494322636

Offset: 1

Farideh Firoozbakht, Dec 10 2004

There is no further term < 3*10^9.

a(11) > 3*10^12. [Donovan Johnson, Jun 14 2009]

			41630193 is in the sequence because 41630193 is the 39103614th composite number.

Cf. A002808, A004086, A100412, A100413, A100415.

Do[s=FromDigits[Reverse[IntegerDigits[n]]];If[s

a(9)-a(10) from Donovan Johnson, Jun 14 2009

A100415 Numbers n such that n is R(n)-th nonprime number, where R(n) is the digit reversal of n (A018252(A004086(n))=n).

Original entry on oeis.org

1, 64, 524, 534, 58725, 907538, 6264385, 9438088, 9596598, 27895162, 422984004, 548911025, 8804661048, 49640253574, 63899981216, 95138721219, 97895906839, 469449672154

Offset: 1

Farideh Firoozbakht, Dec 12 2004

n is in the sequence iff n is not prime and R(n)=n-pi(n). There is no further term up to 3670000000.

a(19) > 10^13. Up to that limit, this sequence contains all the numbers k such that R(k) = k - pi(k). - Giovanni Resta, Aug 08 2019

			548911025 is in the sequence because 548911025 is the 520118945th nonprime natural number.

Cf. A018252, A004086, A100413, A100414, A114926.

Do[s = FromDigits[Reverse[IntegerDigits[n]]]; If[ ! PrimeQ[n] && s == n - PrimePi[n], Print[n]], {n, 548911025}]

a(13)-a(18) from Giovanni Resta, Aug 08 2019

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

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A100414 Numbers n such that n is R(n)-th composite number where R(n) is the digit reversal of n (A002808(A004086(n))=n).

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A100415 Numbers n such that n is R(n)-th nonprime number, where R(n) is the digit reversal of n (A018252(A004086(n))=n).

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