cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-7 of 7 results.

A001020 Powers of 11: a(n) = 11^n.

Original entry on oeis.org

1, 11, 121, 1331, 14641, 161051, 1771561, 19487171, 214358881, 2357947691, 25937424601, 285311670611, 3138428376721, 34522712143931, 379749833583241, 4177248169415651, 45949729863572161, 505447028499293771, 5559917313492231481, 61159090448414546291
Offset: 0

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Author

Keywords

Comments

Same as Pisot sequences E(1, 11), L(1, 11), P(1, 11), T(1, 11). Essentially same as Pisot sequences E(11, 121), L(11, 121), P(11, 121), T(11, 121). See A008776 for definitions of Pisot sequences.
The compositions of n in which each natural number is colored by one of p different colors are called p-colored compositions of n. For n >= 1, a(n) equals the number of 11-colored compositions of n such that no adjacent parts have the same color. - Milan Janjic, Nov 17 2011
a(n), for n <= 4, gives the n-th row of Pascal's triangle (A007318); a(n), n >= 5 "sort of" gives the n-th row of Pascal's triangle, but now the binomial coefficients with more than one digit overlap. - Daniel Forgues, Aug 12 2012
Numbers k such that sigma(11*k) = 11*k + sigma(k). - Jahangeer Kholdi, Nov 13 2013

References

  • N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Programs

Formula

G.f.: 1/(1-11*x).
E.g.f.: exp(11*x).
a(n) = 11*a(n-1), n > 0; a(0)=1. - Philippe Deléham, Nov 23 2008

A097659 a(n) = 1001^n.

Original entry on oeis.org

1, 1001, 1002001, 1003003001, 1004006004001, 1005010010005001, 1006015020015006001, 1007021035035021007001, 1008028056070056028008001, 1009036084126126084036009001, 1010045120210252210120045010001, 1011055165330462462330165055011001, 1012066220495792924792495220066012001
Offset: 0

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Author

Reinhard Zumkeller, Aug 18 2004

Keywords

Comments

694 is the smallest exponent e such that 1001^e begins with a digit greater than 1: A000030(a(694)) = 2, A000030(a(693)) = 1. - Reinhard Zumkeller, Nov 05 2010
a(n) gives the n-th row of Pascal's triangle (A007318) as long as all the binomial coefficients have at most three digits, otherwise the binomial coefficients with more than three digits overlap. - Daniel Forgues, Aug 12 2012

References

  • Rozsa Peter, Playing with Infinity, New York, Dover Publications, 1957.

Crossrefs

Programs

Formula

From Philippe Deléham, Nov 30 2008: (Start)
a(n) = 1001*a(n-1), n > 0; a(0)=1.
G.f.: 1/(1-1001*x). (End)
From Elmo R. Oliveira, Jul 06 2025: (Start)
E.g.f.: exp(1001*x).
a(n) = 91^n * A001020(n). (End)

Extensions

More terms from Elmo R. Oliveira, Jul 06 2025

A185817 Smallest m such that n is a prefix of 101^m in its decimal representation.

Original entry on oeis.org

0, 70, 111, 140, 162, 181, 196, 209, 221, 1, 10, 19, 27, 34, 41, 48, 54, 60, 65, 70, 75, 80, 84, 88, 93, 97, 100, 104, 108, 111, 114, 117, 120, 123, 126, 129, 132, 135, 137, 140, 142, 145, 147, 149, 152, 154, 156, 158, 160, 162, 164, 166, 168, 170, 172, 174, 175, 177, 179, 181
Offset: 1

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Author

Reinhard Zumkeller, Feb 07 2011

Keywords

Comments

a(n) = MIN{e: floor(A096884(e)/10^k) = n for some k}.
a(n) <= a(10*n + d), 0 <= d < 10.

Examples

			a(1) = 0; a(10) = 1; a(101) = 1;
a(2) = 70, as A000030(101^e) = 1 for e < 70 and A000030(101^70) = 2,
101^70=2006763368395383712973746195325904225117468781576180838692428661200863034768\
95435690179367146267108054577096030854694073677909106884264157001.
		

Crossrefs

Programs

  • Haskell
    import Data.List (isPrefixOf)
    a185817 n = pref101pow 0 1 where
       pref101pow e pow101 = if isPrefixOf (show n) (show pow101)
                                then e
                                else pref101pow (e + 1) (101 * pow101)

A291945 Powers of 1111.

Original entry on oeis.org

1, 1111, 1234321, 1371330631, 1523548331041, 1692662195786551, 1880547699518858161, 2089288494165451416871, 2321199517017816524143681, 2578852663406794158323629591, 2865105309044948309897552475601, 3183131998348937572296180800392711, 3536459650165669642821056869236301921, 3929006671334058973174194181721531434231
Offset: 0

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Author

Seiichi Manyama, Mar 09 2018

Keywords

Crossrefs

Powers of ((10^k - 1)/9): A000012 (k=1), A001020 (k=2), A225374 (k=3), this sequence (k=4), A291946 (k=5), A109716 (k=6).
Cf. A096884.

Programs

Formula

a(n) = 1111^n.
G.f.: 1/(1 - 1111*x).
From Elmo R. Oliveira, Aug 16 2024: (Start)
E.g.f.: exp(1111*x).
a(n) = 1111*a(n-1) for n > 0.
a(n) = A001020(n)*A096884(n). (End)

A327926 a(n) = 99^n.

Original entry on oeis.org

1, 99, 9801, 970299, 96059601, 9509900499, 941480149401, 93206534790699, 9227446944279201, 913517247483640899, 90438207500880449001, 8953382542587164451099, 886384871716129280658801, 87752102299896798785221299, 8687458127689783079736908601
Offset: 0

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Author

Eliora Ben-Gurion, Nov 09 2019

Keywords

Examples

			a(4) = 96059601 = 100^4 - 4*100^3 + 6*100^2 - 4*100 + 1 = 100000000 - 4000000 + 60000 - 400 - 1: 100000000 -> 96000000 -> 96060000 -> 96059600 -> 96059601.
a(8) = 99^8 = 9227446944279201.
		

Crossrefs

Formula

a(n) = 99^n.
From Elmo R. Oliveira, Aug 11 2024: (Start)
G.f.: 1/(1-99*x).
E.g.f.: exp(99*x).
a(n) = 99*a(n-1) for n > 0. (End)

A339624 Perfect powers p^k, k >= 2 of palindromic primes p when p^k is not a palindrome.

Original entry on oeis.org

16, 25, 27, 32, 49, 64, 81, 125, 128, 243, 256, 512, 625, 729, 1024, 2048, 2187, 2401, 3125, 4096, 6561, 8192, 15625, 16384, 16807, 17161, 19683, 22801, 32761, 32768, 36481, 59049, 65536, 78125, 97969, 117649, 124609, 131072, 139129, 146689, 161051, 177147, 262144
Offset: 1

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Author

Bernard Schott, Dec 10 2020

Keywords

Comments

Equivalently: numbers m with only one prime factor such that the LCM of their palindromic divisors is neither 1 nor m: subsequence of A334392.
G. J. Simmons conjectured there are no palindromes of form n^k for k >= 5 (and n > 1) (see Simmons p. 98). According to this conjecture, these perfect powers are terms: {2^k, k>=4}, {3^k, k>=3}, {5^k, k>=2}, {7^k, k=2 and k>=4}, {11^k, k>=5}, {101^k, k>= 5}, {131^k, k>=2}, ...
From a(1) = 16 to a(17) = 2187, the data is the same as A056781(10) until A056781(26), then a(18) = 2401 and A056781(27) = 4096.

Examples

			5^2 = 25, 2^6 = 64, 3^4 = 81 are terms.
7^2 = 49 is a term, 7^3 = 343 is not a term, and 7^4 = 2401 is a term.
101^2 = 10201 and 11^4 = 14641 are not terms.
		

References

  • Murray S. Klamkin, Problems in applied mathematics: selections from SIAM review, (1990), p. 520.

Crossrefs

Intersection of A025475 and A334392.
Subsequences: A000079 \ {1,2,4,8}, A000244 \ {1,3,9}, A000351 \ {1,5}, A000420 \ {1,7,343}, A001020 \ {1,11,121,1331,14641}, A096884 \ {1,101, 10201, 1030301, 104060401}.

Programs

  • Mathematica
    q[n_] := Module[{f = FactorInteger[n]}, Length[f] == 1 && f[[1, 2]] > 1 && PalindromeQ[f[[1, 1]]]]; Select[Range[10^5], !PalindromeQ[#] && q[#] &] (* Amiram Eldar, Dec 10 2020 *)
  • PARI
    ispal(n) = my(d=digits(n)); Vecrev(d)==d;
    isok(k) = my(p); isprimepower(k, &p) && isprime(p) && ispal(p) &&!ispal(k); \\ Michel Marcus, Dec 10 2020

Extensions

More terms from Amiram Eldar, Dec 10 2020

A096885 Related to diagonals of Pascal's triangle.

Original entry on oeis.org

1, 100, 10001, 1000200, 100030001, 10004000300, 1000500060001, 100060010000400, 10007001500100001, 1000800210020000500, 100090028003500150001, 10010003600560035000600, 1001100450084007000210001, 100120055012001260056000700, 10013006601650210012600280001, 1001400780220033002520084000800
Offset: 0

Views

Author

Paul Barry, Jul 14 2004

Keywords

Crossrefs

Formula

a(n) = Sum_{k=0..floor(n/2)} binomial(n-k, k)*100^(n-2k).
From Philippe Deléham, Nov 23 2008: (Start)
a(n) = 100*a(n-1) + a(n-2), n > 1; a(0)=1, a(1)=100.
G.f.: 1/(1-100*x-x^2). (End)
E.g.f.: exp(50*x)*(cosh(sqrt(2501)*x) + 50*sinh(sqrt(2501)*x)/sqrt(2501)). - Stefano Spezia, Aug 05 2024

Extensions

a(12)-a(15) from Stefano Spezia, Aug 05 2024
Showing 1-7 of 7 results.