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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A260260 a(n) = n*(16*n^2 - 21*n + 7)/2.

Original entry on oeis.org

0, 1, 29, 132, 358, 755, 1371, 2254, 3452, 5013, 6985, 9416, 12354, 15847, 19943, 24690, 30136, 36329, 43317, 51148, 59870, 69531, 80179, 91862, 104628, 118525, 133601, 149904, 167482, 186383, 206655, 228346, 251504, 276177, 302413, 330260, 359766, 390979
Offset: 0

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Author

Bruno Berselli, Jul 21 2015

Keywords

Comments

Similar sequences, where P(s, m) = ((s-2)*m^2-(s-4)*m)/2 is the m-th s-gonal number:
A000578: P(3, m)*P( 3, m) - P(3, m-1)*P( 3, m-1);
A213772: P(3, m)*P( 4, m) - P(3, m-1)*P( 4, m-1) for m>0;
A005915: P(3, m)*P( 5, m) - P(3, m-1)*P( 5, m-1) " ;
A130748: P(3, m)*P( 6, m) - P(3, m-1)*P( 6, m-1) for m>1;
A027849: P(3, m)*P( 7, m) - P(3, m-1)*P( 7, m-1) for m>0;
A214092: P(3, m)*P( 8, m) - P(3, m-1)*P( 8, m-1) " ;
A100162: P(3, m)*P( 9, m) - P(3, m-1)*P( 9, m-1) " ;
A260260: P(3, m)*P(10, m) - P(3, m-1)*P(10, m-1), this sequence;
A100165: P(3, m)*P(11, m) - P(3, m-1)*P(11, m-1) for m>0.

Crossrefs

Subsequence of A047275.
Sequences of the same type (see comment): A000578, A005915, A027849, A100162, A100165, A130748, A213772, A214092.

Programs

  • Magma
    [n*(16*n^2-21*n+7)/2: n in [0..40]];
  • Mathematica
    Table[n (16 n^2 - 21 n + 7)/2, {n, 0, 40}]
    LinearRecurrence[{4,-6,4,-1},{0,1,29,132},40] (* Harvey P. Dale, May 08 2025 *)
  • PARI
    vector(40, n, n--; n*(16*n^2-21*n+7)/2)
    
  • Sage
    [n*(16*n^2-21*n+7)/2 for n in (0..40)]
    

Formula

G.f.: x*(1 + 25*x + 22*x^2)/(1 - x)^4. [corrected by Georg Fischer, May 10 2019]
a(n) = A000217(n)*A001107(n) - A000217(n-1)*A001107(n-1), with A000217(-1) = 0.
a(n) = A000292(n) + 25*A000292(n-1) + 22*A000292(n-2), with A000292(-2) = A000292(-1) = 0.
a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4) for n >= 4. - Wesley Ivan Hurt, Dec 18 2020
E.g.f.: exp(x)*x*(2 + 27*x + 16*x^2)/2. - Elmo R. Oliveira, Aug 08 2025

A365801 Numbers k such that A163511(k) is a cube.

Original entry on oeis.org

0, 4, 9, 19, 32, 39, 65, 72, 79, 131, 145, 152, 159, 256, 263, 291, 305, 312, 319, 513, 520, 527, 576, 583, 611, 625, 632, 639, 1027, 1041, 1048, 1055, 1153, 1160, 1167, 1216, 1223, 1251, 1265, 1272, 1279, 2048, 2055, 2083, 2097, 2104, 2111, 2307, 2321, 2328, 2335, 2433, 2440, 2447, 2496, 2503, 2531, 2545, 2552
Offset: 1

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Author

Antti Karttunen, Oct 01 2023

Keywords

Comments

The sequence is defined inductively as:
(a) it contains 0 and 4,
and
(b) for any nonzero term a(n), (2*a(n)) + 1 and 8*a(n) are also included as terms.
Because the inductive definition guarantees that all terms after 0 are of the form 7k+2, 7k+4 or 7k+5 (A047378), and because for any n >= 0, n^3 == 0, 1 or 6 (mod 7), (i.e., cubes are in A047275), it follows that there are no cubes in this sequence after the initial 0.

Crossrefs

Positions of multiples of 3 in A365805.
Sequence A243071(n^3), n >= 1, sorted into ascending order.
Subsequence of A047378 (after the initial 0).
Subsequences: A013731, A153894.
Cf. also A365802, A365808.

Programs

  • PARI
    A163511(n) = if(!n, 1, my(p=2, t=1); while(n>1, if(!(n%2), (t*=p), p=nextprime(1+p)); n >>= 1); (t*p));
    isA365801(n) = ispower(A163511(n),3);
    
  • PARI
    isA365801(n) = if(n<=4, !(n%4), if(n%2, isA365801((n-1)/2), if(n%8, 0, isA365801(n/8))));
Showing 1-2 of 2 results.