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 1-10 of 10 results.

A007441 1 + Sum_{n>=1} a_n x^n = Product_{n>=1} (1-x^n)^prime(n).

Original entry on oeis.org

1, -2, -2, 1, 3, 7, 5, 6, -10, -27, -50, -42, -30, 41, 148, 241, 345, 303, 167, -275, -858, -1685, -2342, -2813, -2316, -536, 2914, 8228, 14531, 20955, 24370, 22393, 10265, -13839, -53386, -104364, -161593, -209463, -228141, -188750, -62023, 177547, 541310, 1009998, 1527972, 1976120, 2189974
Offset: 0

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Author

Keywords

References

  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Formula

a(n) = (1/n)*Sum_{k=1..n} a(n-k)*b(k), k>0, a(0)=1, b(k)=-Sum_{d|k} d*prime(d), cf. A061150.

Extensions

Better description from Vladeta Jovovic, Apr 16 2001

A305871 -1 + Product_{n>=1} (1 + x^n)^a(n) = g.f. of A000040 (prime numbers).

Original entry on oeis.org

2, 2, 1, 2, 2, -2, 2, -2, 4, -1, 4, -7, 10, -19, 20, -20, 34, -42, 64, -100, 126, -178, 258, -326, 464, -675, 936, -1371, 1888, -2550, 3690, -5208, 7292, -10467, 14742, -20808, 29610, -41586, 59052, -84438, 119602, -170153, 242256, -343534, 489550, -697815
Offset: 1

Views

Author

Ilya Gutkovskiy, Jun 12 2018

Keywords

Comments

Inverse weigh transform of A000040.

Examples

			(1 + x)^2 * (1 + x^2)^2 * (1 + x^3) * (1 + x^4)^2 * (1 + x^5)^2 * (1 + x^6)^(-2) * ... * (1 + x^n)^a(n) * ... = 1 + 2*x + 3*x^2 + 5*x^3 + 7*x^4 + 11*x^5 + 13*x^6 + ... + A000040(k)*x^k + ...
		

Crossrefs

Programs

  • Maple
    b:= proc(n, i) option remember; `if`(n=0, 1, `if`(i<1, 0,
          add(binomial(a(i), j)*b(n-i*j, i-1), j=0..n/i)))
        end:
    a:= proc(n) option remember; ithprime(n)-b(n, n-1) end:
    seq(a(n), n=1..50);  # Alois P. Heinz, Jun 13 2018
  • Mathematica
    b[n_, i_] := b[n, i] = If[n == 0, 1, If[i < 1, 0,
         Sum[Binomial[a[i], j]*b[n - i*j, i - 1], {j, 0, n/i}]]];
    a[n_] := a[n] = Prime[n] - b[n, n - 1];
    Table[a[n], {n, 1, 50}] (* Jean-François Alcover, Feb 18 2022, after Alois P. Heinz *)

Formula

Product_{n>=1} (1 + x^n)^a(n) = 1 + Sum_{k>=1} prime(k)*x^k.

A061150 a(n) = Sum_{d|n} d*prime(d).

Original entry on oeis.org

2, 8, 17, 36, 57, 101, 121, 188, 224, 353, 343, 573, 535, 729, 777, 1036, 1005, 1406, 1275, 1801, 1669, 2087, 1911, 2861, 2482, 3167, 3005, 3753, 3163, 4541, 3939, 5228, 4879, 5737, 5391, 7314, 5811, 7475, 7063, 8873, 7341, 9957, 8215, 10607, 9849
Offset: 1

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Author

Vladeta Jovovic, Apr 16 2001

Keywords

Examples

			a(4)=36 because the divisors of 4 are 1,2,4 and 1*p(1) + 2*p(2) + 4*p(4) = 1*2 + 2*3 + 4*7 = 36.
		

Crossrefs

Programs

  • Maple
    with(numtheory): a:=proc(n) local div: div:=divisors(n): sum(div[j]*ithprime(div[j]),j=1..tau(n)) end: seq(a(n),n=1..55); # Emeric Deutsch, Jan 20 2007
  • PARI
    a(n) = sumdiv(n, d, d*prime(d)); \\ Michel Marcus, Jun 24 2018

Formula

Equals M * V, where M = A127093 as an infinite lower triangular matrix and V = A000040, the sequence of primes as a vector. E.g., a(4) = 36 = 1*2 + 2*3 + 4*7, where (1, 2, 0, 4) = row 4 of A127093 and 2, 3 and 7 are p(1), p(2), p(4). - Gary W. Adamson, Jan 11 2007
L.g.f.: log(Product_{k>=1} 1/(1 - x^k)^prime(k)) = Sum_{n>=1} a(n)*x^n/n. - Ilya Gutkovskiy, May 10 2017

Extensions

Edited by N. J. A. Sloane, May 04 2007

A061151 1 + Sum_{n>=1} a_n x^n = 1/Product_{n>=1} (1+x^n)^prime(n).

Original entry on oeis.org

1, -2, 0, -3, 5, -3, 14, -4, 25, -32, 16, -88, 18, -155, 108, -153, 393, -88, 855, -160, 1255, -974, 1122, -3172, 370, -6794, 383, -10017, 5004, -9460, 19380, -2635, 45790, 5008, 76263, -7353, 87597, -77967, 48886, -244397, -45016, -500016, -115318, -734277, 56213, -710603, 810177, -161662, 2432173, 910752, 4767086
Offset: 0

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Author

Vladeta Jovovic, Apr 16 2001

Keywords

Crossrefs

Formula

a(n) = (1/n) * Sum_{k=1..n} a(n-k)*b(k), k>0, a(0)=1, b(k)=Sum_{d|k} (-1)^(k/d)*d*prime(d).

A291647 Expansion of Product_{k>=1} (1 + x^prime(k))^prime(k).

Original entry on oeis.org

1, 0, 2, 3, 1, 11, 3, 20, 21, 20, 64, 35, 112, 117, 160, 269, 284, 477, 598, 819, 1116, 1495, 1899, 2718, 3389, 4596, 6121, 7627, 10460, 13128, 17350, 22506, 28696, 37063, 47779, 60249, 78642, 98783, 126058, 160758, 200795, 257750, 321768, 407930, 511526, 640636, 802816, 1005618, 1252820, 1567454, 1946162
Offset: 0

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Author

Ilya Gutkovskiy, Aug 28 2017

Keywords

Comments

Number of partitions of n into distinct prime parts, where prime(k) different parts of size prime(k) are available (2a, 2b, 3a, 3b, 3c, ...).

Examples

			a(6) = 3 because we have [3a, 3b], [3a, 3c] and [3b, 3c].
		

Crossrefs

Programs

  • Mathematica
    nmax = 50; CoefficientList[Series[Product[(1 + x^Prime[k])^Prime[k], {k, 1, nmax}], {x, 0, nmax}], x]

Formula

G.f.: Product_{k>=1} (1 + x^A000040(k))^A000040(k).

A302238 Expansion of Product_{k>=1} ((1 + x^k)/(1 - x^k))^prime(k).

Original entry on oeis.org

1, 4, 14, 46, 136, 382, 1022, 2626, 6530, 15784, 37218, 85842, 194146, 431358, 943038, 2031454, 4316884, 9058662, 18787730, 38542526, 78264298, 157403290, 313712482, 619919350, 1215125262, 2363570168, 4563951858, 8751621598, 16670498062, 31553539214, 59361428202
Offset: 0

Views

Author

Ilya Gutkovskiy, Apr 03 2018

Keywords

Comments

Convolution of the sequences A030009 and A061152.

Crossrefs

Programs

  • Mathematica
    nmax = 30; CoefficientList[Series[Product[((1 + x^k)/(1 - x^k))^Prime[k], {k, 1, nmax}], {x, 0, nmax}], x]

Formula

G.f.: Product_{k>=1} ((1 + x^k)/(1 - x^k))^A000040(k).

A318367 a(n) = Sum_{d|n} (-1)^(n/d+1)*d*prime(d).

Original entry on oeis.org

2, 4, 17, 20, 57, 67, 121, 116, 224, 239, 343, 371, 535, 487, 777, 660, 1005, 958, 1275, 1095, 1669, 1401, 1911, 1715, 2482, 2097, 3005, 2295, 3163, 2987, 3939, 3156, 4879, 3727, 5391, 4502, 5811, 4925, 7063, 5271, 7341, 6619, 8215, 6433, 9849, 7249, 9919, 8691, 11244, 9264
Offset: 1

Views

Author

Ilya Gutkovskiy, Aug 24 2018

Keywords

Crossrefs

Programs

  • Maple
    f:= proc(n) local d; add((-1)^(n/d+1)*d*ithprime(d), d = numtheory:-divisors(n)); end proc:map(f, [$1..100]); # Robert Israel, Aug 01 2023
  • Mathematica
    Table[Sum[(-1)^(n/d + 1) d Prime[d], {d, Divisors[n]}], {n, 50}]
    nmax = 50; Rest[CoefficientList[Series[Sum[k Prime[k] x^k/(1 + x^k), {k, 1, nmax}], {x, 0, nmax}], x]]
    nmax = 50; Rest[CoefficientList[Series[Log[Product[(1 + x^k)^Prime[k], {k, 1, nmax}]], {x, 0, nmax}], x] Range[0, nmax]]
  • PARI
    a(n) = sumdiv(n, d, (-1)^(n/d+1)*d*prime(d)); \\ Michel Marcus, Aug 25 2018

Formula

G.f.: Sum_{k>=1} k*prime(k)*x^k/(1 + x^k).
L.g.f.: log(Product_{k>=1} (1 + x^k)^prime(k)) = Sum_{n>=1} a(n)*x^n/n.

A353169 Expansion of Product_{k>=1} (1 + x^k)^prime(k+1).

Original entry on oeis.org

1, 3, 8, 23, 57, 137, 317, 705, 1524, 3224, 6667, 13521, 26980, 52985, 102624, 196248, 370849, 693159, 1282537, 2350584, 4269912, 7692044, 13748080, 24390170, 42966637, 75187515, 130737631, 225957706, 388279308, 663533206, 1127936772, 1907676978, 3210783522, 5378798428
Offset: 0

Views

Author

Ilya Gutkovskiy, Apr 28 2022

Keywords

Comments

Weigh transform of odd primes.

Crossrefs

Programs

  • Mathematica
    nmax = 33; CoefficientList[Series[Product[(1 + x^k)^Prime[k + 1], {k, 1, nmax}], {x, 0, nmax}], x]
    a[0] = 1; a[n_] := a[n] = (1/n) Sum[Sum[(-1)^(k/d + 1) d Prime[d + 1], {d, Divisors[k]}] a[n - k], {k, 1, n}]; Table[a[n], {n, 0, 33}]

A380613 Expansion of Product_{k>=1} (1 + x^k)^prime(k)#.

Original entry on oeis.org

1, 2, 7, 42, 291, 2970, 36950, 597100, 11070875, 248103940, 7018494836, 215718595582, 7881561212732, 320881902092122, 13754717161317416, 643588827524430916, 33926485821837232397, 1992916854095359256932, 121393059052727838936847, 8107963745977267426512386, 574571379331620422000295082
Offset: 0

Views

Author

Ilya Gutkovskiy, Jan 28 2025

Keywords

Comments

Weigh transform of primorial numbers.

Crossrefs

Programs

  • Maple
    p:= proc(n) option remember; `if`(n<1, 1, p(n-1)*ithprime(n)) end:
    b:= proc(n, i) option remember; `if`(n=0, 1, `if`(i<1, 0,
          add(binomial(p(i), j)*b(n-i*j, i-1), j=0..n/i)))
        end:
    a:= n-> b(n$2):
    seq(a(n), n=0..20);  # Alois P. Heinz, Jan 28 2025
  • Mathematica
    nmax = 20; CoefficientList[Series[Product[(1 + x^k)^Product[Prime[j], {j, 1, k}], {k, 1, nmax}], {x, 0, nmax}], x]
    primorial[n_] := Product[Prime[j], {j, 1, n}]; a[n_] := a[n] = If[n == 0, 1, Sum[Sum[(-1)^(j/d + 1) d primorial[d], {d, Divisors[j]}] a[n - j], {j, 1, n}]/n]; Table[a[n], {n, 0, 20}]

A371308 Expansion of e.g.f. Product_{k>=1} (1 + x^k/k!)^prime(k).

Original entry on oeis.org

1, 2, 5, 23, 101, 511, 3300, 20499, 147249, 1158047, 9284124, 82250155, 762408746, 7406758725, 75928931645, 815389826454, 9127145085135, 106002459387831, 1287304713397098, 16132127163478581, 209381715443456410, 2814011969429674997, 38957100435462040565
Offset: 0

Views

Author

Ilya Gutkovskiy, Mar 24 2024

Keywords

Comments

"EGJ" (unordered, element, labeled) transform of primes.

Crossrefs

Programs

  • Mathematica
    nmax = 22; CoefficientList[Series[Product[(1 + x^k/k!)^Prime[k], {k, 1, nmax}], {x, 0, nmax}], x] Range[0, nmax]!
Showing 1-10 of 10 results.