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 1-4 of 4 results.

A102909 a(n) = Sum_{j=0..8} n^j.

Original entry on oeis.org

1, 9, 511, 9841, 87381, 488281, 2015539, 6725601, 19173961, 48427561, 111111111, 235794769, 469070941, 883708281, 1589311291, 2745954241, 4581298449, 7411742281, 11668193551, 17927094321, 26947368421, 39714002329, 57489010371, 81870575521, 114861197401
Offset: 0

Views

Author

Douglas Winston (douglas.winston(AT)srupc.com), Mar 01 2005

Keywords

Crossrefs

Cf. similar sequences of the type a(n) = Sum_{j=0..m} n^j: A000027 (m=1), A002061 (m=2), A053698 (m=3), A053699 (m=4), A053700 (m=5), A053716 (m=6), A053717 (m=7), this sequence (m=8), A103623 (m=9), A060885 (m=10), A105067 (m=11), A060887 (m=12), A104376 (m=13), A104682 (m=14), A105312 (m=15), A269442 (m=16), A269446 (m=18).

Programs

  • Magma
    [(&+[n^j: j in [0..8]]): n in [0..30]]; // G. C. Greubel, Feb 13 2018
    
  • Mathematica
    1 + Sum[Range[0, 30]^j, {j, 1, 8}] (* G. C. Greubel, Feb 13 2018 *)
    LinearRecurrence[{9,-36,84,-126,126,-84,36,-9,1},{1,9,511,9841,87381,488281,2015539,6725601,19173961},30] (* Harvey P. Dale, Feb 01 2025 *)
  • PARI
    a(n)=n^8+n^7+n^6+n^5+n^4+n^3+n^2+n+1 \\ Charles R Greathouse IV, Oct 07 2015
    
  • Sage
    [sum(n^j for j in (0..8)) for n in (0..30)] # G. C. Greubel, Apr 14 2019

Formula

a(n) = (n^2+n+1) * (n^6+n^3+1) and so is never prime. - Jonathan Vos Post, Dec 21 2012
G.f.: (x^8 + 162*x^7 + 3418*x^6 + 14212*x^5 + 16578*x^4 + 5482*x^3 + 466*x^2 + 1)/(1-x)^9. - Colin Barker, Nov 05 2012, edited by M. F. Hasler, Dec 31 2012
a(n) = (n^9-1)/(n-1) with a(1) = 9. - L. Edson Jeffery and M. F. Hasler, Dec 30 2012
E.g.f.: exp(x)*(1 + 8*x + 247*x^2 + 1389*x^3 + 2127*x^4 + 1206*x^5 + 288*x^6 + 29*x^7 + x^8). - Stefano Spezia, Oct 03 2024

Extensions

Offset corrected by N. J. A. Sloane, Dec 30 2012

A059830 a(n) = n^6 + n^4 + n^2 + 1.

Original entry on oeis.org

1, 4, 85, 820, 4369, 16276, 47989, 120100, 266305, 538084, 1010101, 1786324, 3006865, 4855540, 7568149, 11441476, 16843009, 24221380, 34117525, 47176564, 64160401, 85961044, 113614645, 148316260, 191435329, 244531876, 309373429, 387952660, 482505745, 595531444
Offset: 0

Views

Author

N. J. A. Sloane, Feb 25 2001

Keywords

Crossrefs

Programs

Formula

a(n) = (n^2+1)*(n^4+1) = A002522(n)*A002523(n) = A002522(n)*A002522(n^2). a(n) = (n^8-1)/(n^2-1) = -A024006(n)/A067998(n+1), n>1. - Alexander Adamchuk, Apr 13 2006
G.f.: -(4*x^6+57*x^5+309*x^4+274*x^3+78*x^2-3*x+1)/(x-1)^7. - Colin Barker, Nov 05 2012

A059848 As a square table by antidiagonals, the n-digit number which in base k starts 1010101...

Original entry on oeis.org

0, 0, 1, 0, 1, 0, 0, 1, 1, 1, 0, 1, 2, 2, 0, 0, 1, 3, 5, 2, 1, 0, 1, 4, 10, 10, 3, 0, 0, 1, 5, 17, 30, 21, 3, 1, 0, 1, 6, 26, 68, 91, 42, 4, 0, 0, 1, 7, 37, 130, 273, 273, 85, 4, 1, 0, 1, 8, 50, 222, 651, 1092, 820, 170, 5, 0, 0, 1, 9, 65, 350, 1333, 3255, 4369, 2460, 341, 5, 1, 0, 1, 10
Offset: 0

Views

Author

Henry Bottomley, Feb 26 2001

Keywords

Examples

			T(5,3)=10101 base 3=81+9+1=91; T(4,6)=1010 base 6=216+6=222. Table starts {0,0,0,0,...}, {1,1,1,1,...}, {0,1,2,3,...}, {1,2,5,10,...}, ...
		

Crossrefs

Formula

T(n, k)=floor[k^(n+1)/(k^2-1)] =T(n-2, k)+k^(n-1) =k*T(n-1, k)-((-1)^n-1)/2

A241855 Array t(n,k) of sum of successive even powers of primes, where t(n,k) = sum_(j=0..k-1) prime(n)^(2j), with n>=1 and k>=0, read by ascending antidiagonals.

Original entry on oeis.org

0, 0, 1, 0, 1, 5, 0, 1, 10, 21, 0, 1, 26, 91, 85, 0, 1, 50, 651, 820, 341, 0, 1, 122, 2451, 16276, 7381, 1365, 0, 1, 170, 14763, 120100, 406901, 66430, 5461, 0, 1, 290, 28731, 1786324, 5884901, 10172526, 597871, 21845, 0, 1, 362, 83811, 4855540, 216145205, 288360150, 254313151, 5380840, 87381
Offset: 1

Views

Author

Jean-François Alcover, Apr 30 2014

Keywords

Comments

Conjecture: any term, except 0 and 1, is never a square.
Row n=1 is A002450,
row n=2 is A002452,
row n=3 is A218728,
row n=4 is A218753,
rows n>=5 are not in the OEIS,
column k=2 is A066872,
columns k>=3 are not in the OEIS.

Examples

			Array begins:
0,  1,   5,    21,      85,       341,        1365, ...
0,  1,  10,    91,     820,      7381,       66430, ...
0,  1,  26,   651,   16276,    406901,    10172526, ...
0,  1,  50,  2451,  120100,   5884901,   288360150, ...
0,  1, 122, 14763, 1786324, 216145205, 26153569806, ...
etc.
		

Crossrefs

Programs

  • Mathematica
    t[n_, k_] := ((Prime[n]^2)^k-1)/(Prime[n]^2-1); Table[t[n-k+1, k], {n, 0, 10}, {k, 0, n}] // Flatten

Formula

t(n,k) = ((prime(n)^2)^k-1)/(prime(n)^2-1).
Showing 1-4 of 4 results.