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.

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A017535 a(n) = (12*n+1)^3.

Original entry on oeis.org

1, 2197, 15625, 50653, 117649, 226981, 389017, 614125, 912673, 1295029, 1771561, 2352637, 3048625, 3869893, 4826809, 5929741, 7189057, 8615125, 10218313, 12008989, 13997521, 16194277, 18609625, 21253933, 24137569, 27270901, 30664297, 34328125, 38272753
Offset: 0

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Programs

Formula

G.f.: (1 + 2193*x + 6843*x^2 + 1331*x^3)/(1-x)^4. - Vincenzo Librandi, May 26 2016
a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4), for n>3. - Vincenzo Librandi, May 26 2016
a(n) = A000578(A017533(n)). - Michel Marcus, May 26 2016

A017540 a(n) = (12*n + 1)^8.

Original entry on oeis.org

1, 815730721, 152587890625, 3512479453921, 33232930569601, 191707312997281, 806460091894081, 2724905250390625, 7837433594376961, 19925626416901921, 45949729863572161, 97906861202319841
Offset: 0

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Programs

Formula

a(n) = A001016(A017533(n)). - Michel Marcus, Jul 29 2022

A017543 a(n) = (12*n + 1)^11.

Original entry on oeis.org

1, 1792160394037, 2384185791015625, 177917621779460413, 3909821048582988049, 43513917611435838661, 313726685568359708377, 1673432436896142578125, 7153014030880804126753, 25804264053054077850709, 81402749386839761113321, 230339304218442143770717
Offset: 0

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Author

Keywords

Crossrefs

Cf. A008455 (n^11), A017533 (12n+1).

Programs

Formula

a(n) = A008455(A017533(n)). - Michel Marcus, Jul 28 2015
a(n) = Sum_{k=0..11} binomial(11,k)*(12*n)^k. - Robert Israel, Jul 28 2015

A033576 a(n) = (2*n+1)*(12*n+1).

Original entry on oeis.org

1, 39, 125, 259, 441, 671, 949, 1275, 1649, 2071, 2541, 3059, 3625, 4239, 4901, 5611, 6369, 7175, 8029, 8931, 9881, 10879, 11925, 13019, 14161, 15351, 16589, 17875, 19209, 20591, 22021, 23499, 25025
Offset: 0

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Formula

From Colin Barker, Jun 10 2012: (Start)
a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3).
G.f.: (1 + 36*x + 11*x^2)/(1-x)^3. (End)
a(n) = A005408(n) * A017533(n). - Wesley Ivan Hurt, Feb 02 2014
E.g.f.: (1 + 38*x + 24*x^2)*exp(x). - G. C. Greubel, Oct 12 2019

A110597 Balanced numbers (A020492) k such that k mod 12 = 1.

Original entry on oeis.org

1, 1045, 29029, 50065, 64285, 87685, 1390753, 2011009, 3189625, 7711405, 39298441, 53238625, 68393065, 75416341, 96345613, 225938245, 228404605, 231562825, 233591605, 279999445, 458406445, 462027565, 470527057, 491291125, 513574369, 663605761, 666373825
Offset: 1

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Author

Walter Kehowski, Sep 13 2005

Keywords

Comments

For the first 27 terms, the quotient sigma(n)/phi(n) is 1, 2 or 3.

Crossrefs

Intersection of A017533 and A020492.

Programs

  • Maple
    with(numtheory); BNM1:=[]: for z from 1 to 1 do for m from 0 to 500000 do n:=12*m+1; if sigma(n) mod phi(n) = 0 then BNM1:=[op(BNM1),n] fi; od; od; BNM1;
  • Mathematica
    Select[Range[10^7], Mod[#, 12] == 1 && Divisible[DivisorSigma[1, #], EulerPhi[#]] &] (* Amiram Eldar, Dec 04 2019 *)
  • PARI
    forstep(n=1,1e5,12, if(sigma(n)%eulerphi(n)==0, print1(n", "))) \\ Charles R Greathouse IV, Nov 27 2013

Extensions

a(10)-a(27) from Donovan Johnson, Aug 30 2012

A160080 Lodumo_4 of Fibonacci numbers.

Original entry on oeis.org

0, 1, 5, 2, 3, 9, 4, 13, 17, 6, 7, 21, 8, 25, 29, 10, 11, 33, 12, 37, 41, 14, 15, 45, 16, 49, 53, 18, 19, 57, 20, 61, 65, 22, 23, 69, 24, 73, 77, 26, 27, 81, 28, 85, 89, 30, 31, 93, 32, 97, 101, 34, 35, 105, 36, 109, 113, 38, 39, 117, 40, 121, 125, 42, 43, 129, 44, 133, 137, 46
Offset: 0

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Author

Philippe Deléham, May 01 2009

Keywords

Comments

Permutation of nonnegative numbers.

Crossrefs

Formula

a(n) = lod_4(A000045(n)).
From Philippe Deléham, Nov 30 2023: (Start)
a(n) = 2*a(n-6) - a(n-12) for n >= 12.
a(6*n) = 4*n, a(6*n+1) = 12*n+1, a(6*n+2) = 12*n+5, a(6*n+3) = 4*n+2, a(6*n+4) = 4*n+3, a(6*n+5) = 12*n+9.
G.f.: (x + 5*x^2 + 2*x^3 + 3*x^4 + 9*x^5 + 4*x^6 + 11*x^7 + 7*x^8 + 2*x^9 + x^10 + 3*x^11) / ((1-x)^2*(1+x+x^2)^2*(1+x^3)^2). (End)

A244923 Numbers n such that the digit sum of Fibonacci(n) is equal to the digit sum of Lucas(n).

Original entry on oeis.org

1, 13, 61, 73, 97, 217, 349, 649, 937, 1477, 1513, 1729, 2005, 2077, 2209, 3265, 3649, 3889, 4093, 4609, 4945, 5497, 5749, 5929, 6109, 7309, 7441, 8041, 8389, 8821, 9925, 10525, 10669, 11605, 13201, 13345, 16021, 18529, 18649, 20293, 21481, 22573, 22729, 24169
Offset: 1

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Author

Michel Lagneau, Jul 08 2014

Keywords

Comments

Numbers n such that A004090(n) = A139374(n).
Subsequence of A017533.
It seems that n is odd. The primes of the sequence are: 13, 61, 73, 97, 349, 937, 3889, 4093, 5749, 7309, 8389, 8821, 21481, 22573, 24169, ...
Fibonacci(j) == Lucas(j) (mod 9) iff j == 1 (mod 12), so all a(n) == 1 (mod 12). - Robert Israel, Jul 10 2014

Examples

			13 is in the sequence because Fibonacci(13) = 233, Lucas(13) = 521 and 2+3+3 = 5+2+1 = 8.
		

Crossrefs

Programs

  • Mathematica
    lst={}; Table[If[Total[IntegerDigits[LucasL[n]]] == Total[IntegerDigits[Fibonacci[n]]], AppendTo[lst, n]], {n, 0, 25000}]; lst
    Select[Range[25000],Total[IntegerDigits[Fibonacci[#]]]==Total[IntegerDigits[LucasL[#]]]&] (* Harvey P. Dale, Mar 31 2024 *)

A294031 Numbers k such that k == 1 (mod 12) and 6*k+1, 12*k+1, 18*k+1, 36*k+1, 72*k+1, 108*k+1 and 144*k+1 are all primes, so N = (6*k+1)*(12*k+1)*(18*k+1), (36*k+1)*N, (72*k+1)*N, (108*k+1)*N and (144*k+1)*N are 5 Carmichael numbers in an arithmetic progression.

Original entry on oeis.org

20543425, 80993605, 112608685, 255063865, 307510105, 367621765, 382017685, 400463665, 409631425, 430786405, 536835565, 675787105, 950572525, 1040986765, 1139137825, 1214553025, 1404069205, 1456119805, 1560636805, 1608308905, 1796972905, 1805035225, 1823195605
Offset: 1

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Author

Amiram Eldar, Oct 22 2017

Keywords

Examples

			20543425 generates 11236306070625187487140801 + 8309959597401596721108558352203300 k which are Carmichael numbers for k = 0 to 4.
		

References

  • Andrzej Rotkiewicz, Pseudoprime Numbers and Their Generalizations, Student Association of the Faculty of Sciences, University of Novi Sad, Novi Sad, Yugoslavia, 1972.

Crossrefs

Cf. A002997.
Subsequence of A017533.

Programs

  • Mathematica
    aQ[n_]:=Mod[n,12]==1 && AllTrue[{6n+1, 12n+1, 18n+1, 36n+1, 72n+1, 108n+1, 144n+1}, PrimeQ]; Select[Range[10^8], aQ]

A296180 Triangle read by rows: T(n, k) = 3*(n - k)*k + 1, n >= 0, 0 <= k <= n.

Original entry on oeis.org

1, 1, 1, 1, 4, 1, 1, 7, 7, 1, 1, 10, 13, 10, 1, 1, 13, 19, 19, 13, 1, 1, 16, 25, 28, 25, 16, 1, 1, 19, 31, 37, 37, 31, 19, 1, 1, 22, 37, 46, 49, 46, 37, 22, 1, 1, 25, 43, 55, 61, 61, 55, 43, 25, 1, 1, 28, 49, 64, 73, 76, 73, 64, 49, 28, 1
Offset: 0

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Author

Wolfdieter Lang, Dec 20 2017

Keywords

Comments

This is member m = 3 of the family of triangles T(m; n, k) = m*(n - k)*k + 1, for m >= 0. For m = 0: A000012(n, k) (read as a triangle); for m = 1: A077028 (rascal), for m = 2: T(2, n+1, k+1) = A130154(n, k). Motivated by A130154 to look at this family of triangles.
In general the recurrence is: T(m; n, 0) = 1 and T(m; n, n) = 1 for n >= 0; T(m; n, k) = (T(m; n-1, k-1)*T(m; n-1, k) + m)/T(m; n-2, k-1), for n >= 2, k = 1..n-1.
The general g.f. of the sequence of column k (with leading zeros) is G(m; k, x) = (x^k/(1 - x)^2)*(1 + (m*k - 1)*x), k >= 0.
The general g.f. of the triangle T(m;, n, k) is GT(m; x, t) = (1 - (1 + t)*x + (m+1)*t*x^2)/((1 - t*x)*(1 - x))^2, and G(m; k, x) = (d/dt)^k GT(m; x, t)/k!|_{t=0}.
For a simple combinatorial interpretation see the one given in A130154 by Rogério Serôdio which can be generalized to m >= 3.

Examples

			The triangle T(n, k) begins:
n\k   0  1  2  3  4  5  6  7  8  9 10 ...
0:    1
1:    1  1
2:    1  4  1
3:    1  7  7  1
4:    1 10 13 10  1
5:    1 13 19 19 13  1
6:    1 16 25 28 25 16  1
7:    1 19 31 37 37 31 19  1
8:    1 22 37 46 49 46 37 22  1
9:    1 25 43 55 61 61 55 43 25  1
10:   1 28 49 64 73 76 73 64 49 28  1
...
Recurrence: 28 = T(6, 3) = (19*19 + 3)/13 = 28.
		

Crossrefs

Columns (without leading zeros): A000012, A016777, A016921, A016921, A017173, A017533, ...

Programs

  • Mathematica
    Table[3 k (n - k) + 1, {n, 0, 10}, {k, 0, n}] // Flatten (* Michael De Vlieger, Dec 20 2017 *)
  • PARI
    lista(nn) = for(n=0, nn, for(k=0, n, print1(3*(n - k)*k + 1, ", "))) \\ Iain Fox, Dec 21 2017

Formula

T(n, k) = 3*(n - k)*k + 1, n >= 0, 0 <= k <= n,
Recurrence: T(n, 0) = 1 and T(n, n) = 1 for n >= 0; T(n, k) = (T(n-1, k-1)*T(n-1, k) + 3)/T(n-2, k-1), for n >= 2, k = 1..n-1.
G.f. of column k (with leading zeros): (x^k/(1 - x)^2)*(1 + (3*k-1)*x), k >= 0.
G.f. of triangle: (1 - (1 + t)*x + 4*t*x^2)/((1 - t*x)*(1 - x))^2 = 1 + (1+t)*x +(1 + 4*t + t^2)*x^2 + (1 + 7*t + 7*t^2 + t^3)*x^3 = ...

A387404 Numbers of the form 12*k + 1 that satisfy Euler's condition for odd perfect numbers (A228058).

Original entry on oeis.org

325, 637, 925, 1525, 1573, 1813, 1825, 2425, 2725, 2989, 3577, 3757, 3925, 4477, 4525, 4693, 4753, 4825, 5341, 5725, 6025, 6253, 6877, 6925, 7381, 7693, 7825, 8125, 8425, 8725, 8833, 8869, 9325, 9457, 9925, 10225, 10309, 10525, 10693, 10825, 10933, 11221, 11425, 11737, 11809, 12337, 12493, 13189, 13357, 13525, 13573
Offset: 1

Views

Author

Antti Karttunen, Aug 29 2025

Keywords

Crossrefs

Intersection of A017533 and A228058.

Programs

  • Mathematica
    nn = 51; n = 1; t = {}; While[Length[t] < nn, n = n + 2; {p, e} = Transpose[FactorInteger[n]]; od = Select[e, OddQ]; If[Length[e] > 1 && Length[od] == 1 && Mod[od[[1]], 4] == 1 && Mod[p[[Position[e, od[[1]]][[1, 1]]]], 4] == 1&&Mod[n,12]==1, AppendTo[t, n]]]; t (* James C. McMahon, Aug 29 2025 *)
  • PARI
    is_A387404(n) = if(1!=(n%12) || (omega(n)<2), 0, my(f=factor(n), y=0); for(i=1, #f~, if(1==(f[i, 2]%4), if((1==y)||(1!=(f[i, 1]%4)), return(0), y=1), if(f[i, 2]%2, return(0)))); (y));
Previous Showing 31-40 of 41 results. Next