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.

Previous Showing 31-40 of 52 results. Next

A321483 a(n) = 7*2^n + (-1)^n.

Original entry on oeis.org

8, 13, 29, 55, 113, 223, 449, 895, 1793, 3583, 7169, 14335, 28673, 57343, 114689, 229375, 458753, 917503, 1835009, 3670015, 7340033, 14680063, 29360129, 58720255, 117440513, 234881023, 469762049, 939524095, 1879048193, 3758096383, 7516192769, 15032385535
Offset: 0

Views

Author

Paul Curtz, Nov 11 2018

Keywords

Comments

Difference table:
8, 13, 29, 55, 113, 223, 449, ...
5, 16, 26, 58, 110, 226, 446, 898, ...
11, 10, 32, 52, 116, 220, 452, 892, 1796, ...
-1, 22, 20, 64, 104, 232, 440, 904, 1784, 3592, ...
-2, 44, 40, 128, 208, 464, 880, 1808, 3568, 7184, ...
etc.
Every diagonal is a sequence of the form k*2^m.
a(n) is divisible by
. 5 if n is a term of A004767,
. 11 if n is a term of A016885,
. 13 if n is a term of A017533.

Crossrefs

Programs

  • Mathematica
    a[n_] := 7*2^n + (-1)^n ; Array[a, 32, 0] (* Amiram Eldar, Nov 12 2018 *)
    CoefficientList[Series[E^-x + 7 E^(2 x), {x, 0, 20}], x]*Table[n!, {n, 0, 20}] (* Stefano Spezia, Nov 12 2018 *)
    LinearRecurrence[{1,2},{8,13},40] (* Harvey P. Dale, Mar 18 2022 *)
  • PARI
    Vec((8 + 5*x) / ((1 + x)*(1 - 2*x)) + O(x^40)) \\ Colin Barker, Nov 11 2018

Formula

O.g.f.: (8 + 5*x) / ((1 + x)*(1 - 2*x)). - Colin Barker, Nov 11 2018
E.g.f.: exp(-x) + 7*exp(2*x). - Stefano Spezia, Nov 12 2018
a(n) = a(n-1) + 2*a(n-2).
a(n) = 2*a(n-1) + 3*(-1)^n for n>0, a(0)=8.
a(2*k) = 7*4^k + 1, a(2*k+1) = 14*4^k - 1.
a(n) = A014551(n) + A014551(n-1) + A014551(n-2).
a(n) = 2^(n+3) - 3*A001045(n).
a(n) mod 9 = A070366(n+3).
a(n) + a(n+1) = 21*2^n.

Extensions

Two terms corrected, and more terms added by Colin Barker, Nov 11 2018

A330613 Triangle read by rows: T(n, k) = 1 + k - 2*n - 2*k*n + 2*n^2, with 0 <= k < n.

Original entry on oeis.org

1, 5, 2, 13, 8, 3, 25, 18, 11, 4, 41, 32, 23, 14, 5, 61, 50, 39, 28, 17, 6, 85, 72, 59, 46, 33, 20, 7, 113, 98, 83, 68, 53, 38, 23, 8, 145, 128, 111, 94, 77, 60, 43, 26, 9, 181, 162, 143, 124, 105, 86, 67, 48, 29, 10, 221, 200, 179, 158, 137, 116, 95, 74, 53, 32, 11
Offset: 1

Views

Author

Stefano Spezia, Dec 20 2019

Keywords

Comments

T(n, k) is the k-th super- and subdiagonal sum of the matrix M(n) whose permanent is A330287(n).

Examples

			n\k|   0   1   2   3   4   5
---+------------------------
1  |   1
2  |   5   2
3  |  13   8   3
4  |  25  18  11   4
5  |  41  32  23  14   5
6  |  61  50  39  28  17   6
...
For n = 3 the matrix M is
      1, 2, 3
      2, 4, 6
      3, 6, 8
and therefore T(3, 0) = 1 + 4 + 8 = 13, T(3, 1) = 2 + 6 = 8 and T(3, 2) = 3.
		

Crossrefs

Cf. A000027: diagonal; A001105: 2nd column; A001844: 1st column; A016789: 1st subdiagonal; A016885: 2nd subdiagonal; A017029: 3rd subdiagonal; A017221: 4th subdiagonal; A017461: 5th subdiagonal; A081436: row sums; A132209: 3rd column; A164284: 7th subdiagonal; A269044: 6th subdiagonal.

Programs

  • Mathematica
    Flatten[Table[1+k-2n-2k*n+2n^2,{n,1,11},{k,0,n-1}]] (* or *)
    r[n_] := Table[SeriesCoefficient[(1-x*(2-5x+2(1+x)y))/((1-x)^3*(1-y)^2), {x, 0, i}, {y, 0, j}], {i, n, n}, {j, 0, n-1}]; Flatten[Array[r, 11]] (* or *)
    r[n_] := Table[SeriesCoefficient[Exp[x+y]*(1+2x(x-y)+y), {x, 0, i}, {y, 0, j}]*i!*j!, {i, n, n}, {j, 0, n-1}]; Flatten[Array[r, 11]]

Formula

O.g.f.: (1 - x*(2 - 5*x + 2*(1 + x)*y))/((1 - x)^3*(1 - y)^2).
E.g.f.: exp(x+y)*(1 + 2*x*(x - y) + y).
T(n, k) = A001844(n-1) - k*A005408(n-1), with 0 <= k < n. [Typo corrected by Stefano Spezia, Feb 14 2020]

A013856 a(n) = 10^(5*n + 3).

Original entry on oeis.org

1000, 100000000, 10000000000000, 1000000000000000000, 100000000000000000000000, 10000000000000000000000000000, 1000000000000000000000000000000000, 100000000000000000000000000000000000000, 10000000000000000000000000000000000000000000, 1000000000000000000000000000000000000000000000000
Offset: 0

Views

Author

Keywords

Crossrefs

Subsequence of A011557.
Cf. A016885.

Programs

  • Magma
    [10^(5*n+3): n in [0..10]]; // Vincenzo Librandi, Jul 08 2011
    
  • Mathematica
    10^(5*Range[0, 10] + 3) (* Paolo Xausa, Mar 04 2025 *)
  • Maxima
    makelist(10^(5*n+3),n,0,20); /* Martin Ettl, Oct 21 2012 */

Formula

From Elmo R. Oliveira, Mar 02 2025: (Start)
G.f.: 1000/(1 - 100000*x).
E.g.f.: 1000*exp(100000*x).
a(n) = A011557(A016885(n)). (End)

A013896 a(n) = 20^(5*n + 3).

Original entry on oeis.org

8000, 25600000000, 81920000000000000, 262144000000000000000000, 838860800000000000000000000000, 2684354560000000000000000000000000000, 8589934592000000000000000000000000000000000, 27487790694400000000000000000000000000000000000000
Offset: 0

Views

Author

Keywords

Crossrefs

Subsequence of A009964.

Programs

  • Magma
    [20^(5*n+3): n in [0..10]]; // Vincenzo Librandi, May 27 2011
  • Mathematica
    20^(5Range[0,20]+3) (* or *) NestList[3200000#&,8000,20] (* Harvey P. Dale, Dec 05 2021 *)

Formula

a(n) = 3200000*a(n-1), a(0)=8000. - Vincenzo Librandi, May 27 2011
From Elmo R. Oliveira, Jul 11 2025: (Start)
G.f.: 8000/(1-3200000*x).
E.g.f.: 8000*exp(3200000*x).
a(n) = A013824(n)*A013856(n) = A009964(A016885(n)). (End)

A154614 Triangle read by rows where T(m,n) = m*n + m + n - 1, 1<=n<=m.

Original entry on oeis.org

2, 4, 7, 6, 10, 14, 8, 13, 18, 23, 10, 16, 22, 28, 34, 12, 19, 26, 33, 40, 47, 14, 22, 30, 38, 46, 54, 62, 16, 25, 34, 43, 52, 61, 70, 79, 18, 28, 38, 48, 58, 68, 78, 88, 98, 20, 31, 42, 53, 64, 75, 86, 97, 108, 119, 22, 34, 46, 58, 70, 82, 94, 106, 118, 130, 142
Offset: 1

Views

Author

Vincenzo Librandi, Jan 16 2009

Keywords

Comments

T(m,n)+2 = (n+1)*(m+1) is not prime.
T(m,m)+2 = (m+1)^2.
First column: A005843; second column: A112414; third column: 2*A020742; fourth column: A016885. - Vincenzo Librandi, Nov 17 2012

Examples

			Triangle begins:
2;
4, 7;
6, 10, 14;
8, 13, 18, 23;
10, 16, 22, 28, 34;
12, 19, 26, 33, 40, 47;
14, 22, 30, 38, 46, 54, 62;
16, 25, 34, 43, 52, 61, 70, 79;
18, 28, 38, 48, 58, 68, 78, 88, 98;
20, 31, 42, 53, 64, 75, 86, 97, 108, 119; etc.
		

Crossrefs

Programs

  • Magma
    [(n*k + n + k - 1): k in [1..n], n in [1..11]]; // Vincenzo Librandi, Nov 17 2012
  • Mathematica
    t[n_,k_]:=n*k + n + k - 1; Table[t[n, k], {n, 10}, {k, n}]//Flatten (* Vincenzo Librandi, Nov 17 2012 *)

A186041 Numbers of the form 3*k + 2, 5*k + 3, or 7*k + 4.

Original entry on oeis.org

2, 3, 4, 5, 8, 11, 13, 14, 17, 18, 20, 23, 25, 26, 28, 29, 32, 33, 35, 38, 39, 41, 43, 44, 46, 47, 48, 50, 53, 56, 58, 59, 60, 62, 63, 65, 67, 68, 71, 73, 74, 77, 78, 80, 81, 83, 86, 88, 89, 92, 93, 95, 98, 101, 102, 103, 104, 107, 108, 109, 110, 113, 116, 118, 119, 122
Offset: 1

Views

Author

Klaus Brockhaus, Feb 11 2011, Mar 09 2011

Keywords

Comments

n is in the sequence iff n is in A016789 or in A016885 or in A017029.
First differences are periodic with period length 57. Least common multiple of 3, 5, 7 is 105; number of terms <= 105 is 57.
Sequence is not essentially the same as A053726: a(n) = A053726(n-3) for 3 < n < 33, a(34)=62, A053726(34-3)=61.
Sequence is not essentially the same as A104275: a(n) = A104275(n-2) for 3 < n < 33, a(34)=62, A104275(34-3)=61.

Crossrefs

Programs

  • Magma
    IsA186041:=func< n | exists{ k: k in [0..n div 3] | n in [3*k+2, 5*k+3, 7*k+4] } >; [ n: n in [1..200] | IsA186041(n) ];
  • Mathematica
    Take[With[{no=50},Union[Join[3Range[0,no]+2,5Range[0,no]+3,7Range[0,no]+4]]],70]  (* Harvey P. Dale, Feb 16 2011 *)

Formula

a(n) = a(n-57) + 105.
a(n) = a(n-1) + a(n-57) - a(n-58).
G.f.: x*(x^57 + x^56 + x^55 + x^54 + 3*x^53 + 3*x^52 + 2*x^51 + x^50 + 3*x^49 + x^48 + 2*x^47 + 3*x^46 + 2*x^45 + x^44 + 2*x^43 + x^42 + 3*x^41 + x^40 + 2*x^39 + 3*x^38 + x^37 + 2*x^36 + 2*x^35 + x^34 + 2*x^33 + x^32 + x^31 + 2*x^30 + 3*x^29 + 3*x^28 + 2*x^27 + x^26 + x^25 + 2*x^24 + x^23 + 2*x^22 + 2*x^21 + x^20 + 3*x^19 + 2*x^18 + x^17 + 3*x^16 + x^15 + 2*x^14 + x^13 + 2*x^12 + 3*x^11 + 2*x^10 + x^9 + 3*x^8 + x^7 + 2*x^6 + 3*x^5 + 3*x^4 + x^3 + x^2 + x + 2) / ((x - 1)^2*(x^2 + x + 1)*(x^18 + x^17 + x^16 + x^15 + x^14 + x^13 + x^12 + x^11 + x^10 + x^9 + x^8 + x^7 + x^6 + x^5 + x^4 + x^3 + x^2 + x + 1)*(x^36 - x^35 + x^33 - x^32 + x^30 - x^29 + x^27 - x^26 + x^24 - x^23 + x^21 - x^20 + x^18 - x^16 + x^15 - x^13 + x^12 - x^10 + x^9 - x^7 + x^6 - x^4 + x^3 - x + 1)).

A186042 Numbers of the form 2*k + 1, 3*k + 2, or 5*k + 3.

Original entry on oeis.org

1, 2, 3, 5, 7, 8, 9, 11, 13, 14, 15, 17, 18, 19, 20, 21, 23, 25, 26, 27, 28, 29, 31, 32, 33, 35, 37, 38, 39, 41, 43, 44, 45, 47, 48, 49, 50, 51, 53, 55, 56, 57, 58, 59, 61, 62, 63, 65, 67, 68, 69, 71, 73, 74, 75, 77, 78, 79, 80, 81, 83, 85, 86, 87, 88, 89, 91, 92, 93, 95, 97
Offset: 1

Views

Author

Klaus Brockhaus, Feb 11 2011, Mar 09 2011

Keywords

Comments

n is in the sequence iff n is in A005408 or in A016789 or in A016885.
First differences are periodic with period length 22. Least common multiple of 2, 3, 5 is 30; number of terms <= 30 is 22.

Crossrefs

Programs

  • Magma
    IsA186042:=func< n | exists{ k: k in [0..n div 2] | n in [2*k+1, 3*k+2, 5*k+3] } >; [ n: n in [1..100] | IsA186042(n) ];
    
  • Mathematica
    LinearRecurrence[{2,-2,2,-2,2,-2,2,-2,2,-2,2,-2,2,-2,2,-2,2,-2,2,-2,2,-1},{1,2,3,5,7,8,9,11,13,14,15,17,18,19,20,21,23,25,26,27,28,29},71] (* Ray Chandler, Jul 12 2015 *)
  • PARI
    isok(n) = (n % 2) || ((n % 3)==2) || ((n % 5)==3); \\ Michel Marcus, Jul 26 2017

Formula

a(n) = a(n-22) + 30.
a(n) = a(n-1) + a(n-22) - a(n-23).
G.f.: x*(x^21 + x^19 + x^17 + x^16 + x^15 + x^13 + x^11 + x^10 + x^8 + x^7 + x^6 + x^4 + x^3 + x^2 + 1) / ((x - 1)^2*(x^10 - x^9 + x^8 - x^7 + x^6 - x^5 + x^4 - x^3 + x^2 - x + 1)*(x^10 + x^9 + x^8 + x^7 + x^6 + x^5 + x^4 + x^3 + x^2 + x + 1)).

A279895 a(n) = n*(5*n + 11)/2.

Original entry on oeis.org

0, 8, 21, 39, 62, 90, 123, 161, 204, 252, 305, 363, 426, 494, 567, 645, 728, 816, 909, 1007, 1110, 1218, 1331, 1449, 1572, 1700, 1833, 1971, 2114, 2262, 2415, 2573, 2736, 2904, 3077, 3255, 3438, 3626, 3819, 4017, 4220, 4428, 4641, 4859, 5082, 5310, 5543, 5781, 6024, 6272, 6525
Offset: 0

Views

Author

Bruno Berselli, Dec 22 2016

Keywords

Crossrefs

Second bisection of A165720.
The first differences are in A016885.
Cf. similar sequences provided by P(s,m)+s*m, where P(s,m) = ((s-2)*m^2-(s-4)*m)/2 is the m-th s-gonal number: A008585 (s=2), A055999 (s=3), A028347 (s=4), A140091 (s=5), A033537 (s=6), this sequence (s=7), A067725 (s=8).

Programs

  • Magma
    [n*(5*n+11)/2: n in [0..60]];
  • Mathematica
    Table[n (5 n + 11)/2, {n, 0, 60}]
    LinearRecurrence[{3,-3,1},{0,8,21},60] (* Harvey P. Dale, Nov 14 2022 *)
  • PARI
    vector(60, n, n--; n*(5*n+11)/2)
    
  • Python
    [n*(5*n+11)/2 for n in range(60)]
    
  • Sage
    [n*(5*n+11)/2 for n in range(60)]
    

Formula

O.g.f.: x*(8 - 3*x)/(1 - x)^3.
E.g.f.: x*(16 + 5*x)*exp(x)/2.
a(n+h) - a(n-h) = h*A017281(n+1), with h>=0. A particular case:
a(n) - a(-n) = 11*n = A008593(n).
a(n+h) + a(n-h) = 2*a(n) + A033429(h), with h>=0. A particular case:
a(n) + a(-n) = A033429(n).
a(n) - a(n-2) = A017281(n) for n>1. Also:
40*a(n) + 121 = A017281(n+1)^2.
a(n) = A000566(n) + 7*n, also a(n) = A000566(n) + A008589(n). - Michel Marcus, Dec 22 2016

A319524 a(n) is the smallest number that belongs simultaneously to the two arithmetic progressions prime(n) + m*prime(n+1) and prime(n+1) + m*prime(n+2), m >= 1, n >= 1.

Original entry on oeis.org

8, 33, 40, 128, 115, 302, 226, 226, 835, 401, 734, 1718, 1030, 842, 3121, 3475, 1401, 2339, 5108, 1969, 3233, 2486, 6491, 9692, 10298, 5560, 11552, 6211, 4177, 7987, 6022, 18763, 16678, 21893, 8001, 25585, 13523, 9682, 30961, 32035, 7057, 36089, 19105, 39002, 7162, 47041, 50163, 51752
Offset: 1

Views

Author

Keywords

Comments

Construct a table T in which T(m,n) = prime(n) + m*prime(n+1) as shown below. Then a(n) is defined as the smallest number appearing both in column n and column n+1, so a(1)=8, a(2)=33, a(3)=40, etc.
.
m\n| 1 2 3 4 5 6 7 8 ...
----+--------------------------------------------------
1 | 5 --8 12 18 24 30 36 42 ...
|
2 | 8-- 13 19 29 37 47 55 65 ...
|
3 | 11 18 26 40 50 64 74 88 ...
| /
4 | 14 23 33 / 51 63 81 93 111 ...
| / /
5 | 17 28 / 40- 62 76 98 112 134 ...
| /
6 | 20 33- 47 73 89 115 131 157 ...
| /
7 | 23 38 54 84 102 / 132 150 180 ...
| /
8 | 26 43 61 95 115 149 169 203 ...
|
9 | 29 48 68 106 128 166 188 226 ...
| / /
10 | 32 53 75 117 / 141 183 207 / 249 ...
| / /
11 | 35 58 82 128 154 200 226 272 ...
|
12 | 38 63 89 139 167 217 245 295 ...
|
13 | 41 68 96 150 180 234 264 318 ...
|
14 | 44 73 103 161 193 251 283 341 ...
|
15 | 47 78 110 172 206 268 302 364 ...
| /
16 | 50 83 117 183 219 285 / 321 387 ...
| /
17 | 53 88 124 194 232 302 340 410 ...
|
... |... ... ... ... ... ... ... ... ...
Conjectures:
1. There are infinitely many pairs of consecutive equal terms. (Note that the first pair is (a(7), a(8)).)
2. There exists no N such that the sequence is monotonic for n > N.
From Amiram Eldar, Sep 22 2018: (Start)
Theorem 1: The intersection of the two mentioned arithmetic progressions is always nonempty.
Corollary: The sequence is infinite. (End)
Sequences that derive from this:
1. Positions in {s(n)} at which a(n) occurs: (2,6,5,11,8,17,19,...).
2. Positions in {s(n+1)} at which a(n) occurs: (1,4,3,9,6,15,15,...).
3. Differences between these two sequences: (1,2,2,2,2,4,...).

Crossrefs

Programs

  • GAP
    P:=Filtered([1..10000],IsPrime);;
    T:=List([1..Length(P)-1],n->List([1..Length(P)-1],m->P[n]+m*P[n+1]));;
    a:=List([1..50],k->Minimum(List([1..Length(T)-1],i->Intersection(T[i],T[i+1]))[k])); # Muniru A Asiru, Sep 26 2018
  • Mathematica
    a[n_]:=ChineseRemainder[{Prime[n],Prime[n+1]},{Prime[n+1],Prime[n+2]} ];Array[a,44] (* Amiram Eldar, Sep 22 2018 *)

Extensions

Table from Jon E. Schoenfield, Sep 23 2018
More terms from Amiram Eldar, Sep 22 2018

A354935 Row 5 of A354940: Numbers k for which A345992(k) = 5, divided by 5.

Original entry on oeis.org

3, 6, 8, 11, 13, 16, 23, 26, 31, 36, 41, 43, 46, 51, 53, 56, 61, 71, 73, 81, 83, 86, 91, 96, 101, 103, 106, 113, 116, 121, 128, 131, 141, 146, 151, 163, 166, 171, 173, 176, 181, 191, 193, 196, 206, 211, 223, 226, 233, 241, 243, 251, 256, 263, 271, 276, 281, 283, 293, 301, 311, 313, 321, 326, 331, 343, 346, 353, 356, 361
Offset: 1

Views

Author

Antti Karttunen, Jun 15 2022

Keywords

Comments

Apparently, all terms are either of the form 5k+1 (in A016861), or of the form 5k+3 (in A016885).

Crossrefs

Programs

  • Mathematica
    q[n_] := Module[{m = 1}, While[!Divisible[m*(m + 1), 5*n], m++]; GCD[5*n, m] == 5]; Select[Range[360], q] (* Amiram Eldar, Jun 17 2022 *)
  • PARI
    A354935(n) = A354940sq(5,n);
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