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 21-30 of 30 results.

A168392 a(n) = 5 + 8*floor((n-1)/2).

Original entry on oeis.org

5, 5, 13, 13, 21, 21, 29, 29, 37, 37, 45, 45, 53, 53, 61, 61, 69, 69, 77, 77, 85, 85, 93, 93, 101, 101, 109, 109, 117, 117, 125, 125, 133, 133, 141, 141, 149, 149, 157, 157, 165, 165, 173, 173, 181, 181, 189, 189, 197, 197, 205, 205, 213, 213, 221, 221, 229, 229
Offset: 1

Views

Author

Vincenzo Librandi, Nov 24 2009

Keywords

Crossrefs

Programs

  • Magma
    [5+8*Floor((n-1)/2): n in [1..70]]; // Vincenzo Librandi, Sep 18 2013
  • Mathematica
    RecurrenceTable[{a[1]==5,a[n]==8n-a[n-1]-6},a,{n,80}] (* or *) LinearRecurrence[{1,1,-1},{5,5,13},80] (* or *) With[{c= LinearRecurrence[ {2,-1},{5,13},40]}, Riffle[c,c]] (* Harvey P. Dale, Jan 27 2013 *)
    Table[5 + 8 Floor[(n - 1)/2], {n, 60}] (* Bruno Berselli, Sep 18 2013 *)
    CoefficientList[Series[(5 + 3 x^2)/((1 + x) (x - 1)^2),{x, 0, 70}], x] (* Vincenzo Librandi, Sep 18 2013 *)

Formula

a(n) = 8*n - a(n-1) - 6 with n>1, a(1)=5.
a(1) = 5, a(2)=5, a(3)=13; for n>3, a(n) = a(n-1) +a(n-2) -a(n-3). - Harvey P. Dale, Jan 27 2013
G.f.: x*(5 + 3*x^2)/((1+x)*(x-1)^2). - Vincenzo Librandi, Sep 18 2013
E.g.f.: (-2 + 3*exp(x) + (4*x - 1)*exp(2*x))*exp(-x). - G. C. Greubel, Jul 19 2016
a(n) = A168379(n) - 2. - Filip Zaludek, Nov 01 2016

Extensions

New definition by Vincenzo Librandi, Sep 18 2013

A175462 Number of divisors of integers of the form 5 + 8n.

Original entry on oeis.org

2, 2, 4, 2, 2, 6, 2, 2, 4, 4, 4, 4, 2, 2, 6, 4, 4, 4, 2, 2, 8, 2, 2, 8, 2, 4, 4, 4, 2, 4, 6, 4, 6, 2, 2, 8, 2, 4, 4, 2, 6, 6, 4, 2, 8, 4, 2, 4, 2, 2, 10, 4, 2, 8, 4, 4, 4, 2, 4, 6, 4, 4, 4, 2, 4, 12, 4, 2, 6, 2, 4, 4, 4, 4, 4, 6, 2, 8, 4, 6, 8, 2, 2, 4, 2, 4, 12, 2, 2, 4, 6, 2, 8, 4, 2, 12, 2, 4, 4, 2, 8, 4, 2
Offset: 0

Views

Author

Zak Seidov, May 23 2010

Keywords

Comments

All terms are even.

Crossrefs

Cf. A004770 (Numbers of form 8n + 5), A007521 (Primes of form 8n + 5). A000005 (d(n) : number of divisors of n), A001620.

Programs

  • Maple
    map(numtheory:-tau,[seq(i,i=5..1000,8)]); # Robert Israel, Mar 20 2020
  • Mathematica
    Table[DivisorSigma[0, 8*n + 5], {n, 0, 100}] (* Amiram Eldar, Jan 14 2024 *)
  • PARI
    a(n) = numdiv(5+8*n); \\ Michel Marcus, Oct 15 2013

Formula

a(n) = d(5 + 8*n).
a(n) = A000005(A004770(n)).
Sum_{k=1..n} a(k) ~ (n/2) * (log(n) + 2*gamma - 1 + 5*log(2)), where gamma is Euler's constant (A001620). - Amiram Eldar, Jan 14 2024

A177065 a(n) = (8*n+3)*(8*n+5).

Original entry on oeis.org

15, 143, 399, 783, 1295, 1935, 2703, 3599, 4623, 5775, 7055, 8463, 9999, 11663, 13455, 15375, 17423, 19599, 21903, 24335, 26895, 29583, 32399, 35343, 38415, 41615, 44943, 48399, 51983, 55695, 59535, 63503, 67599, 71823, 76175, 80655, 85263, 89999, 94863, 99855
Offset: 0

Views

Author

Vincenzo Librandi, May 31 2010

Keywords

Comments

Cf. comment of Reinhard Zumkeller in A177059: in general, (h*n+h-k)*(h*n+k) = h^2*A002061(n+1) + (h-k)*k - h^2; therefore a(n) = 64*A002061(n+1) - 49. - Bruno Berselli, Aug 24 2010

Crossrefs

Programs

Formula

a(n) = 128*n + a(n-1) with n > 0, a(0)=15.
a(n) = A125169(A016754(n) - 1). - Reinhard Zumkeller, Jul 05 2010
a(0)=15, a(1)=143, a(2)=399, a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3). - Harvey P. Dale, Mar 13 2013
G.f.: (15+98*x+15*x^2)/(1-x)^3. - Vincenzo Librandi, Apr 08 2013
From Amiram Eldar, Feb 19 2023: (Start)
a(n) = A017101(n)*A004770(n).
Sum_{n>=0} 1/a(n) = (sqrt(2)-1)*Pi/16.
Sum_{n>=0} (-1)^n/a(n) = (cos(Pi/8) * log(tan(3*Pi/16)) + sin(Pi/8) * log(cot(Pi/16)))/4.
Product_{n>=0} (1 - 1/a(n)) = sec(Pi/8)*cos(Pi/(4*sqrt(2))).
Product_{n>=0} (1 + 1/a(n)) = sec(Pi/8). (End)
E.g.f.: exp(x)*(15 + 64*x*(2 + x)). - Elmo R. Oliveira, Oct 25 2024

Extensions

Edited by N. J. A. Sloane, Jun 22 2010

A265228 Interleave the even numbers with the numbers that are congruent to {1, 3, 7} mod 8.

Original entry on oeis.org

0, 1, 2, 3, 4, 7, 6, 9, 8, 11, 10, 15, 12, 17, 14, 19, 16, 23, 18, 25, 20, 27, 22, 31, 24, 33, 26, 35, 28, 39, 30, 41, 32, 43, 34, 47, 36, 49, 38, 51, 40, 55, 42, 57, 44, 59, 46, 63, 48, 65, 50, 67, 52, 71, 54, 73, 56, 75, 58, 79, 60, 81, 62, 83, 64, 87, 66
Offset: 0

Views

Author

Paul Curtz, Dec 06 2015

Keywords

Comments

b(n) denotes the sequence:
0, 0, 0, 0, 0, 0, 1, -1, 1, -1, 1, -1, 1, 2, -2, 2, -2, 2, -2, 2, 3, -3, 3, -3, 3, -3, 3, 4, -4, ..., and
c(n) = n + b(n) = n + floor((n+1)/7)*(-1)^((n+1) mod 7) provides:
0, 1, 2, 3, 4, 5, 7, 6, 9, 8, 11, 10, 13, 15, 12, 17, 14, 19, 16, 21, 23, 18, 25, 20, 27, 22, 29, ..., which is a permutation of A001477.
a(n) differs from c(n) because c(n) contains the terms of the form 8*k+5.

Crossrefs

Programs

  • Mathematica
    lim = 11; Riffle[Range[0, 6 lim, 2], Select[Range[8 lim], MemberQ[{1, 3, 7}, Mod[#, 8]] &]] (* Michael De Vlieger, Dec 06 2015 *)
  • PARI
    concat(0, Vec(x*(1+2*x+2*x^2+2*x^3+4*x^4+2*x^5+x^6)/((1-x)^2 *(1+x)^2*(1-x+x^2)*(1+x+x^2)) + O(x^100))) \\ Colin Barker, Dec 06 2015
    
  • PARI
    vector(100, n, n--; n+(1-(-1)^n)*floor(n/6+1/3)) \\ Altug Alkan, Dec 09 2015

Formula

a(n) = n + 2*A260160(n) = n + (1-(-1)^n)*floor(n/6+1/3). Therefore, for odd n, a(n) = A047529((n+1)/2); otherwise, a(n) = n.
a(n) = a(n-6) - (-1)^n + 7.
a(n) = A260708(n) - A260699(n-1) - A079979(n+3), with A260699(-1) = 0.
From Colin Barker, Dec 06 2015: (Start)
a(n) = a(n-2) + a(n-6) - a(n-8) for n > 7.
G.f.: x*(1+2*x+2*x^2+2*x^3+4*x^4+2*x^5+x^6) / ((1-x)^2*(1+x)^2*(1-x+x^2)*(1+x+x^2)). (End)

A137194 Lucky numbers (A000959) which are congruent to 5 mod 8.

Original entry on oeis.org

13, 21, 37, 69, 93, 133, 141, 189, 205, 237, 261, 285, 349, 357, 421, 429, 477, 517, 541, 613, 621, 645, 685, 693, 717, 741, 781, 805, 885, 925, 933, 957, 981, 997, 1021, 1029, 1053, 1093, 1101, 1117, 1189, 1197, 1245, 1261, 1285, 1309, 1357, 1365, 1389, 1485
Offset: 1

Views

Author

N. J. A. Sloane, Mar 07 2008

Keywords

Crossrefs

Intersection of A000959 and A004770.

A146302 a(n) = (8*n+5)*(8*n+9).

Original entry on oeis.org

45, 221, 525, 957, 1517, 2205, 3021, 3965, 5037, 6237, 7565, 9021, 10605, 12317, 14157, 16125, 18221, 20445, 22797, 25277, 27885, 30621, 33485, 36477, 39597, 42845, 46221, 49725, 53357, 57117, 61005, 65021, 69165, 73437, 77837, 82365
Offset: 0

Views

Author

Miklos Kristof, Oct 29 2008

Keywords

Comments

From Miklos Kristof, Nov 03 2008: (Start)
f(y) = y^4*(1 + y^4) = y^4 - y^8 + y^12 - y^16 + y^20 - y^24 + ...
Integral_{y} f(y) dy = y^5/5 - y^9/9 + y^13/13 - y^17/17 + y^21/21 - y^25/25 + ...
Integral_{y=0..1} f(y) dy = 1/5 - 1/9 + 1/13 - 1/17 + 1/21 - 1/25 + ...
= (9 - 5)/(5*9) + (17 - 13)/(13*17) + (25 - 21)/(21*25) + ...
= 4/(5*9) + 4/(13*17) + 4/(21*25) + ...
Integral_{y=0..1} f(y) dy = Sum_{m>=0} 4/((8*m+5)*(8*m+9))
= -(1/8)*sqrt(2)*Pi + 1 - (1/4)*sqrt(2)*log(1+sqrt(2))
= 0.13302701266008896241... (End)

Programs

  • Maple
    seq((8*m+5)*(8*m+9),m=0..40); # Miklos Kristof, Nov 03 2008
  • Mathematica
    Table[(8n+5)(8n+9),{n,0,40}] (* or *) LinearRecurrence[{3,-3,1},{45,221,525},40] (* Harvey P. Dale, Oct 10 2015 *)
  • PARI
    a(n)=(8*n+5)*(8*n+9) \\ Charles R Greathouse IV, Jun 17 2017

Formula

G.f: (45 + 86*x - 3*x^2)/(1-x)^3.
E.g.f.: (45 + 176*x + 64*x^2)*exp(x).
a(n) = A004770(n) * A004768(n). - Reinhard Zumkeller, Oct 30 2008

A303273 Array T(n,k) = binomial(n, 2) + k*n + 1 read by antidiagonals.

Original entry on oeis.org

1, 1, 1, 1, 2, 2, 1, 3, 4, 4, 1, 4, 6, 7, 7, 1, 5, 8, 10, 11, 11, 1, 6, 10, 13, 15, 16, 16, 1, 7, 12, 16, 19, 21, 22, 22, 1, 8, 14, 19, 23, 26, 28, 29, 29, 1, 9, 16, 22, 27, 31, 34, 36, 37, 37, 1, 10, 18, 25, 31, 36, 40, 43, 45, 46, 46, 1, 11, 20, 28, 35, 41
Offset: 0

Views

Author

Keywords

Comments

Columns are linear recurrence sequences with signature (3,-3,1).
8*T(n,k) + A166147(k-1) are squares.
Columns k are binomial transforms of [1, k, 1, 0, 0, 0, ...].
Antidiagonals sums yield A116731.

Examples

			The array T(n,k) begins
1    1    1    1    1    1    1    1    1    1    1    1    1  ...  A000012
1    2    3    4    5    6    7    8    9   10   11   12   13  ...  A000027
2    4    6    8   10   12   14   16   18   20   22   24   26  ...  A005843
4    7   10   13   16   19   22   25   28   31   34   37   40  ...  A016777
7   11   15   19   23   27   31   35   39   43   47   51   55  ...  A004767
11  16   21   26   31   36   41   46   51   56   61   66   71  ...  A016861
16  22   28   34   40   46   52   58   64   70   76   82   88  ...  A016957
22  29   36   43   50   57   64   71   78   85   92   99  106  ...  A016993
29  37   45   53   61   69   77   85   93  101  109  117  125  ...  A004770
37  46   55   64   73   82   91  100  109  118  127  136  145  ...  A017173
46  56   66   76   86   96  106  116  126  136  146  156  166  ...  A017341
56  67   78   89  100  111  122  133  144  155  166  177  188  ...  A017401
67  79   91  103  115  127  139  151  163  175  187  199  211  ...  A017605
79  92  105  118  131  144  157  170  183  196  209  222  235  ...  A190991
...
The inverse binomial transforms of the columns are
1    1    1    1    1    1    1    1    1    1    1    1    1  ...
0    1    2    3    4    5    6    7    8    9   10   11   12  ...
1    1    1    1    1    1    1    1    1    1    1    1    1  ...
0    0    0    0    0    0    0    0    0    0    0    0    0  ...
0    0    0    0    0    0    0    0    0    0    0    0    0  ...
0    0    0    0    0    0    0    0    0    0    0    0    0  ...
...
T(k,n-k) = A087401(n,k) + 1 as triangle
1
1   1
1   2   2
1   3   4   4
1   4   6   7   7
1   5   8  10  11  11
1   6  10  13  15  16  16
1   7  12  16  19  21  22  22
1   8  14  19  23  26  28  29  29
1   9  16  22  27  31  34  36  37  37
1  10  18  25  31  36  40  43  45  46  46
...
		

References

  • R. L. Graham, D. E. Knuth and O. Patashnik, Concrete Mathematics: A Foundation for Computer Science, Addison-Wesley, 1994.

Crossrefs

Programs

  • Maple
    T := (n, k) -> binomial(n, 2) + k*n + 1;
    for n from 0 to 20 do seq(T(n, k), k = 0 .. 20) od;
  • Mathematica
    Table[With[{n = m - k}, Binomial[n, 2] + k n + 1], {m, 0, 11}, {k, m, 0, -1}] // Flatten (* Michael De Vlieger, Apr 21 2018 *)
  • Maxima
    T(n, k) := binomial(n, 2)+ k*n + 1$
    for n:0 thru 20 do
        print(makelist(T(n, k), k, 0, 20));
    
  • PARI
    T(n,k) = binomial(n, 2) + k*n + 1;
    tabl(nn) = for (n=0, nn, for (k=0, nn, print1(T(n, k), ", ")); print); \\ Michel Marcus, May 17 2018

Formula

G.f.: (3*x^2*y - 3*x*y + y - 2*x^2 + 2*x - 1)/((x - 1)^3*(y - 1)^2).
E.g.f.: (1/2)*(2*x*y + x^2 + 2)*exp(y + x).
T(n,k) = 3*T(n-1,k) - 3*T(n-2,k) + T(n-3,k), with T(0,k) = 1, T(1,k) = k + 1 and T(2,k) = 2*k + 2.
T(n,k) = T(n-1,k) + n + k - 1.
T(n,k) = T(n,k-1) + n, with T(n,0) = 1.
T(n,0) = A152947(n+1).
T(n,1) = A000124(n).
T(n,2) = A000217(n).
T(n,3) = A034856(n+1).
T(n,4) = A052905(n).
T(n,5) = A051936(n+4).
T(n,6) = A246172(n+1).
T(n,7) = A302537(n).
T(n,8) = A056121(n+1) + 1.
T(n,9) = A056126(n+1) + 1.
T(n,10) = A051942(n+10) + 1, n > 0.
T(n,11) = A101859(n) + 1.
T(n,12) = A132754(n+1) + 1.
T(n,13) = A132755(n+1) + 1.
T(n,14) = A132756(n+1) + 1.
T(n,15) = A132757(n+1) + 1.
T(n,16) = A132758(n+1) + 1.
T(n,17) = A212427(n+1) + 1.
T(n,18) = A212428(n+1) + 1.
T(n,n) = A143689(n) = A300192(n,2).
T(n,n+1) = A104249(n).
T(n,n+2) = T(n+1,n) = A005448(n+1).
T(n,n+3) = A000326(n+1).
T(n,n+4) = A095794(n+1).
T(n,n+5) = A133694(n+1).
T(n+2,n) = A005449(n+1).
T(n+3,n) = A115067(n+2).
T(n+4,n) = A133694(n+2).
T(2*n,n) = A054556(n+1).
T(2*n,n+1) = A054567(n+1).
T(2*n,n+2) = A033951(n).
T(2*n,n+3) = A001107(n+1).
T(2*n,n+4) = A186353(4*n+1) (conjectured).
T(2*n,n+5) = A184103(8*n+1) (conjectured).
T(2*n,n+6) = A250657(n-1) = A250656(3,n-1), n > 1.
T(n,2*n) = A140066(n+1).
T(n+1,2*n) = A005891(n).
T(n+2,2*n) = A249013(5*n+4) (conjectured).
T(n+3,2*n) = A186384(5*n+3) = A186386(5*n+3) (conjectured).
T(2*n,2*n) = A143689(2*n).
T(2*n+1,2*n+1) = A143689(2*n+1) (= A030503(3*n+3) (conjectured)).
T(2*n,2*n+1) = A104249(2*n) = A093918(2*n+2) = A131355(4*n+1) (= A030503(3*n+5) (conjectured)).
T(2*n+1,2*n) = A085473(n).
a(n+1,5*n+1)=A051865(n+1) + 1.
a(n,2*n+1) = A116668(n).
a(2*n+1,n) = A054569(n+1).
T(3*n,n) = A025742(3*n-1), n > 1 (conjectured).
T(n,3*n) = A140063(n+1).
T(n+1,3*n) = A069099(n+1).
T(n,4*n) = A276819(n).
T(4*n,n) = A154106(n-1), n > 0.
T(2^n,2) = A028401(n+2).
T(1,n)*T(n,1) = A006000(n).
T(n*(n+1),n) = A211905(n+1), n > 0 (conjectured).
T(n*(n+1)+1,n) = A294259(n+1).
T(n,n^2+1) = A081423(n).
T(n,A000217(n)) = A158842(n), n > 0.
T(n,A152947(n+1)) = A060354(n+1).
floor(T(n,n/2)) = A267682(n) (conjectured).
floor(T(n,n/3)) = A025742(n-1), n > 0 (conjectured).
floor(T(n,n/4)) = A263807(n-1), n > 0 (conjectured).
ceiling(T(n,2^n)/n) = A134522(n), n > 0 (conjectured).
ceiling(T(n,n/2+n)/n) = A051755(n+1) (conjectured).
floor(T(n,n)/n) = A133223(n), n > 0 (conjectured).
ceiling(T(n,n)/n) = A007494(n), n > 0.
ceiling(T(n,n^2)/n) = A171769(n), n > 0.
ceiling(T(2*n,n^2)/n) = A046092(n), n > 0.
ceiling(T(2*n,2^n)/n) = A131520(n+2), n > 0.

A047436 Numbers that are congruent to {5, 6} mod 8.

Original entry on oeis.org

5, 6, 13, 14, 21, 22, 29, 30, 37, 38, 45, 46, 53, 54, 61, 62, 69, 70, 77, 78, 85, 86, 93, 94, 101, 102, 109, 110, 117, 118, 125, 126, 133, 134, 141, 142, 149, 150, 157, 158, 165, 166, 173, 174, 181, 182, 189, 190
Offset: 1

Views

Author

Keywords

Crossrefs

Union of A004770 and A017137.

Programs

  • Mathematica
    Select[Range[200], MemberQ[{5, 6}, Mod[#, 8]] &] (* Amiram Eldar, Dec 19 2021 *)

Formula

From Vincenzo Librandi, Aug 06 2010: (Start)
a(n) = a(n-1) + a(n-2) - a(n-3).
a(n) = 8*n - a(n-1) - 5, n > 1. (End)
G.f. x*(5+x+2*x^2) / ( (1+x)*(x-1)^2 ). - R. J. Mathar, Dec 07 2011
Sum_{n>=1} (-1)^(n+1)/a(n) = (2-sqrt(2))*Pi/16 + log(2)/8 - sqrt(2)*log(sqrt(2)+1)/8. - Amiram Eldar, Dec 19 2021

A175486 Composite numbers of form 8n+5 with all prime factors of form 8m+5.

Original entry on oeis.org

125, 325, 725, 845, 925, 1325, 1525, 1885, 2197, 2405, 2525, 2725, 3125, 3445, 3725, 3925, 3965, 4205, 4325, 4525, 4901, 4925, 5365, 5725, 6253, 6565, 6725, 6845, 6925, 7085, 7325, 7685, 7925, 8125, 8725, 8845, 8957, 9325, 9685, 9725, 9805, 9925, 10205
Offset: 1

Views

Author

Zak Seidov, May 27 2010

Keywords

Comments

There are no squares and no semiprimes in the sequence.

Examples

			125=5^3, 325=5^2*13, 725=5^2*29.
		

Crossrefs

Cf. A004770 Numbers of form 8n+5, A175461 Semiprimes of form 8n+5, A007521 Primes of form 8n+5.

Programs

  • Mathematica
    Do[nn=8n+5;If[ !PrimeQ[nn]&&{5}==Union[Mod[(fi=First/@FactorInteger[nn]),8]],Print[nn]],{n,2*10^3}]

A360033 Table T(n,k), n >= 1 and k >= 0, read by antidiagonals, related to Jacobsthal numbers A001045.

Original entry on oeis.org

1, 2, 1, 3, 3, 3, 4, 5, 7, 5, 5, 7, 11, 13, 11, 6, 9, 15, 21, 27, 21, 7, 11, 19, 29, 43, 53, 43, 8, 13, 23, 37, 59, 85, 107, 85, 9, 15, 27, 45, 75, 117, 171, 213, 171, 10, 17, 31, 53, 91, 149, 235, 341, 427, 341, 11, 19, 35, 61, 107, 181, 299, 469
Offset: 1

Views

Author

Philippe Deléham, Jan 22 2023

Keywords

Examples

			The array T(n,k), for n <= 1 and k >= 0, begins:
n = 1: 1,  1,  3,  5,  11,  21,  43, ... -> A001045(k+1)
n = 2: 2,  3,  7, 13,  27,  53, 107, ... -> A048573(k)
n = 3: 3,  5, 11, 21,  43,  85, 171, ... -> A001045(k+3)
n = 4: 4,  7, 15, 29,  59, 117, 235, ... -> ?
n = 5: 5,  9, 19, 37,  75, 149, 299, ... -> A062092(k+1)
n = 6: 6, 11, 23, 45,  91, 181, 363, ... -> ?
n = 7: 7, 13, 27, 53, 107, 213, 427, ... -> A048573(k+2)
		

Crossrefs

Columns: A000027, A005408, A004767, A004770, A106839 for k = 0, 1, 2, 3, 4.

Formula

T(n,k) = T(1,k) + (n-1)*2^k.
T(n,k) = 2*T(n, k-1) + (-1)^k.
T(n,k) = T(n-1,k) + 2^k.
T(n,k) = 2^k * n - A001045(k).
T(n,k) = T(n,k-1) +2*T(n,k-2).
Previous Showing 21-30 of 30 results.