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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A130533 a(n) = smallest k such that A001358(n+1) = A001358(n) + (A001358(n) mod k), or 0 if no such k exists.

Original entry on oeis.org

0, 0, 2, 6, 13, 9, 2, 19, 2, 19, 2, 3, 4, 37, 8, 43, 47, 47, 53, 2, 6, 59, 61, 8, 71, 6, 79, 2, 5, 83, 89, 2, 3, 12, 101, 107, 4, 3, 3, 2, 11
Offset: 1

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Author

Rémi Eismann, Aug 16 2007 - Jan 20 2011

Keywords

Comments

a(n) is the "weight" of semiprimes.
The decomposition of semiprimes into weight * level + gap is A001358(n) = a(n) * A184729(n) + A065516(n) if a(n) > 0.

Examples

			For n = 1 we have A001358(n) = 4, A001358(n+1) = 6; there is no k such that 6 - 4 = 2 = (4 mod k), hence a(1) = 0.
For n = 3 we have A001358(n) = 9, A001358(n+1) = 10; 2 is the smallest k such that 10 - 9 = 1 = (9 mod k), hence a(3) = 2.
For n = 19 we have A001358(n) = 55, A001358(n+1) = 57; 53 is the smallest k such that 57 - 55 = 2 = (55 mod k), hence a(19) = 53.
		

Crossrefs

A130650 a(n) = smallest k such that A014612(n+1) = A014612(n) + (A014612(n) mod k), or 0 if no such k exists.

Original entry on oeis.org

0, 0, 4, 13, 2, 13, 18, 4, 43, 8, 3, 41, 4, 4, 3, 13, 2, 37, 16, 43, 97, 4, 9, 10, 53, 4, 5, 10, 3, 6, 61, 43, 2, 11, 2, 12, 163, 8, 13, 2, 5, 173, 8, 89, 4, 3, 37, 61, 101, 101, 107, 229, 113
Offset: 1

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Author

Rémi Eismann, Aug 16 2007 - Jan 21 2011

Keywords

Comments

a(n) is the "weight" of 3-almost primes.
The decomposition of 3-almost primes into weight * level + gap is A014612(n) = a(n) * A184753(n) + A114403(n) if a(n) > 0.

Examples

			For n = 1 we have A014612(1) = 8, A014612(2) = 12; there is no k such that 12 - 8 = 4 = (8 mod k), hence a(1) = 0.
For n = 3 we have A014612(3) = 18, A014612(4) = 20; 4 is the smallest k such that 20 - 18 = 2 = (18 mod k), hence a(3) = 4.
For n = 21 we have A014612(21) = 98, A014612(22) = 99; 97 is the smallest k such that 99 - 98 = 1 = (97 mod k), hence a(21) = 97.
		

Crossrefs

A130703 a(n) = smallest k such that A000217(n+1) = A000217(n) + (A000217(n) mod k), or 0 if no such k exists.

Original entry on oeis.org

0, 0, 0, 0, 9, 14, 10, 27, 35, 22, 18, 65, 77, 18, 26, 119, 27, 38, 34, 27, 209, 46, 28, 55, 299, 36, 35, 377, 45, 62, 58, 45, 527, 40, 54, 629, 95, 54, 74, 779, 63, 86, 82, 63, 989, 94, 54, 161, 235, 68, 91, 265, 81, 65, 106, 81, 145, 118, 90, 1769, 1829
Offset: 1

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Author

Rémi Eismann, Aug 16 2007 - Jan 10 2011

Keywords

Comments

a(n) is the weight of triangular numbers.
The decomposition of triangular numbers into weight * level + gap is A000217(n) = a(n) * A184219(n) + (n + 1) if a(n) > 0.

Examples

			For n = 1 we have A000217(n) = 1, A000217(n+1) = 3; there is no k such that 3 - 1 = 2 = (1 mod k), hence a(1) = 0.
For n = 5 we have A000217(n) = 15, A000217(n+1) = 21; 9 is the smallest k such that 21 - 15 = 6 = (15 mod k), hence a(5) = 9.
For n = 22 we have A000217(n) = 253, A000217(n+1) = 276; 46 is the smallest k such that 276 - 253 = 23 = (253 mod k), hence a(22) = 46.
		

Crossrefs

A130882 a(n) = smallest k such that A002808(n+1) = A002808(n) + (A002808(n) mod k), or 0 if no such k exists.

Original entry on oeis.org

0, 4, 7, 2, 4, 5, 13, 2, 7, 4, 19, 2, 4, 23, 2, 5, 2, 13, 4, 31, 2, 3, 2, 17, 37, 2, 19, 4, 43, 2, 4, 47, 2, 7, 2, 5, 53, 2, 5, 2, 4, 29, 61, 2, 3, 2, 4, 67, 2, 4, 5, 73, 2, 3, 2, 4, 79, 2, 4, 83, 2, 5, 2, 43, 89, 2, 7, 2, 3, 2, 47, 97
Offset: 1

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Author

Rémi Eismann, Aug 21 2007 - Jan 09 2011

Keywords

Comments

a(n) is the "weight" of composite numbers.
The decomposition of composite numbers into weight * level + gap is A002808(n) = a(n) * A179621(n) + A073783(n) if a(n) > 0.

Examples

			For n = 1 we have A002808(n) = 4, A002808(n+1) = 6; there is no k such that 6 - 4 = 2 = (4 mod k), hence a(1) = 0.
For n = 3 we have A002808(n) = 8, A002808(n+1) = 9; 7 is the smallest k such that 9 - 8 = 1 = (8 mod k), hence a(3) = 7.
For n = 24 we have A002808(n) = 36, A002808(n+1) = 38; 17 is the smallest k such that 38 - 36 = 2 = (36 mod k), hence a(24) = 17.
		

Crossrefs

A130889 a(n) = smallest k such that A000959(n+1) = A000959(n) + (A000959(n) mod k), or 0 if no such k exists.

Original entry on oeis.org

0, 0, 5, 5, 11, 9, 17, 19, 29, 29, 31, 37, 47, 13, 59, 5, 5, 71, 71, 71, 9, 29, 31, 9, 107, 103, 5, 5, 131, 43, 131, 11, 5, 157, 167, 51, 5, 191, 7, 197, 199, 29, 5, 43, 227, 233, 233, 223, 257, 15, 9, 263, 281, 281, 281, 97, 13, 59, 317, 7, 17, 17, 47, 11, 353, 71, 349, 379, 389
Offset: 1

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Author

Rémi Eismann, Aug 21 2007 - Jan 23 2011

Keywords

Comments

a(n) is the "weight" of lucky numbers.
The decomposition of lucky numbers into weight * level + gap is A000959(n) = a(n) * A184828(n) + A031883(n) if a(n) > 0.

Examples

			For n = 1 we have A000959(n) = 1, A000959(n+1) = 3; there is no k such that 3 - 1 = 2 = (1 mod k), hence a(1) = 0.
For n = 3 we have A000959(n) = 7, A000959(n+1) = 9; 5 is the smallest k such that 9 - 7 = 2 = (7 mod k), hence a(3) = 5.
For n = 24 we have A000959(n) = 105, A000959(n+1) = 111; 9 is the smallest k such that 111 - 105 = 6 = (105 mod k), hence a(24) = 9.
		

Crossrefs

A117873 Primes for which the level as defined in A117563 is 3.

Original entry on oeis.org

11, 19, 37, 43, 97, 113, 127, 139, 163, 223, 307, 313, 317, 337, 389, 397, 401, 421, 457, 479, 547, 673, 691, 709, 757, 761, 853, 863, 883, 929, 937, 953, 1021, 1051, 1109, 1297, 1303, 1327, 1399, 1471, 1567, 1571, 1583, 1693, 1699, 1723, 1783, 1951, 2029
Offset: 1

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Author

Rémi Eismann, May 02 2006

Keywords

Examples

			13 = 11 + 11 mod 3 = 11 + 11 mod 9, level = 3
701 = 691 + 691 mod 227 = 691 + 691 mod 681, level = 3
6907 = 6899 + 6899 mod 2297 = 6899 + 6899 mod 6891, level = 3
		

Crossrefs

Programs

  • Mathematica
    f[n_] := Block[{d, j = 2, p = Prime@n}, d = Prime[n + 1] - p; While[j < p && Mod[p, j] != d, j++ ]; If[j == p, 0, j]]; g[n_] := Block[{d, k = p = Prime@n}, d = Prime[n + 1] - p; While[k > 0 && Mod[p, k] != d, k-- ]; If[k == 0, 0, k]]; h[n_] := Block[{a = f@n, b = g@n}, If[a == 0, 0, b/a]]; Prime@Select[ Range@327, h@# == 3 &] (* Robert G. Wilson v *)

Extensions

More terms from Robert G. Wilson v, May 06 2006

A184752 a(n) = largest k such that A014612(n+1) = A014612(n) + (A014612(n) mod k), or 0 if no such k exists.

Original entry on oeis.org

0, 0, 16, 13, 26, 26, 18, 40, 43, 40, 48, 41, 60, 64, 66, 65, 74, 74, 64, 86, 97, 96, 99, 100, 106, 112, 115, 110, 123, 120, 122, 129, 146, 143, 152, 144, 163, 160, 169, 170, 170, 173, 168, 178, 184, 186, 185, 183, 202, 202, 214
Offset: 1

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Author

Rémi Eismann, Jan 21 2011

Keywords

Comments

From the definition, a(n) = A014612(n) - A114403(n) if A014612(n) - A114403(n) > A114403(n), 0 otherwise where A014612 are the 3-almost primes and A114403 are the gaps between 3-almost primes.

Examples

			For n = 1 we have A014612(1) = 8, A014612(2) = 12; there is no k such that 12 - 8 = 4 = (8 mod k), hence a(1) = 0.
For n = 3 we have A014612(3) = 18, A014612(4) = 20; 16 is the largest k such that 20 - 18 = 2 = (18 mod k), hence a(3) = 16.
For n = 21 we have A014612(21) = 98, A014612(22) = 99; 97 is the largest k such that 99 - 98 = 1 = (97 mod k), hence a(21) = 97.
		

Crossrefs

A133150 a(n) = smallest k such that A000290(n+1) = A000290(n) + (A000290(n) mod k), or 0 if no such k exists.

Original entry on oeis.org

0, 0, 0, 0, 14, 23, 17, 47, 31, 79, 49, 119, 71, 167, 97, 223, 127, 41, 46, 359, 199, 439, 241, 527, 82, 89, 337, 727, 391, 839, 449, 137, 73, 1087, 577, 1223, 647, 1367, 103, 217, 94, 1679, 881, 1847, 967, 119, 151, 2207, 1151, 2399, 1249, 113, 193, 401, 1457
Offset: 1

Views

Author

Rémi Eismann, Sep 22 2007 - Jan 10 2011

Keywords

Comments

a(n) is the "weight" of squares (A000290).
The decomposition of squares into weight * level + gap is A000217(n) = a(n) * A184221(n) + A005408(n) if a(n) > 0.

Examples

			For n = 1 we have A000290(n) = 1, A000290(n+1) = 4; there is no k such that 4 - 1 = 3 = (1 mod k), hence a(1) = 0.
For n = 5 we have A000290(n) = 25, A000290(n+1) = 36; 14 is the smallest k such that 36 - 25 = 11 = (25 mod k), hence a(5) = 14.
For n = 18 we have A000290(n) = 324, A000290(n+1) = 361; 41 is the smallest k such that 361 - 324 = 37 = (324 mod k), hence a(18) = 41.
		

Crossrefs

A133151 a(n) = smallest k such that A000326(n+1) = A000326(n) + (A000326(n) mod k), or 0 if no such k exists.

Original entry on oeis.org

0, 0, 0, 0, 19, 32, 24, 67, 89, 38, 71, 173, 69, 61, 71, 109, 373, 211, 79, 529, 587, 72, 89, 779, 283, 461, 499, 359, 1159, 311, 111, 1423, 1517, 269, 857, 1817, 641, 127, 134, 251, 2377, 1249, 138, 2749, 2879, 251, 787, 173, 381, 1787, 1861, 1291
Offset: 1

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Author

Rémi Eismann, Sep 22 2007 - Jan 21 2011

Keywords

Comments

a(n) is the "weight" of pentagonal numbers (A000326).
The decomposition of pentagonal numbers into weight * level + gap is A000326(n) = a(n) * A184751(n) + A016777(n) if a(n) > 0.

Examples

			For n = 1 we have A000326(n) = 1, A000326(n+1) = 5; there is no k such that 5 - 1 = 4 = (1 mod k), hence a(1) = 0.
For n = 5 we have A000326(n) = 35, A000326(n+1) = 51; 19 is the smallest k such that 51 - 35 = 16 = (35 mod k), hence a(5) = 19.
For n = 18 we have A000326(n) = 477, A000326(n+1) = 532; 211 is the smallest k such that 532 - 477 = 55 = (477 mod k), hence a(18) = 211.
		

Crossrefs

A179621 a(n) = A179620(n)/A130882(n) unless A130882(n) = 0 in which case a(n) = 0.

Original entry on oeis.org

0, 1, 1, 4, 2, 2, 1, 7, 2, 4, 1, 10, 5, 1, 12, 5, 13, 2, 7, 1, 16, 11, 17, 2, 1, 19, 2, 10, 1, 22, 11, 1, 24, 7, 25, 10, 1, 27, 11, 28, 14, 2, 1, 31, 21, 32, 16, 1, 34, 17, 14, 1, 37, 25, 38, 19, 1, 40, 20, 1, 42, 17, 43, 2, 1, 45, 13, 46, 31, 47, 2, 1, 49, 14, 25, 1, 52, 26, 2, 1
Offset: 1

Views

Author

Rémi Eismann, Jan 09 2011

Keywords

Comments

a(n) is the "level" of composite numbers.
The decomposition of composite numbers into weight * level + gap is A002808(n) = A130882(n) * a(n) + A073783(n) if a(n) > 0.
A179620(n) = A002808(n) - A073783(n) if A002808(n) - A073783(n) > A073783(n), 0 otherwise.

Examples

			For n = 1 we have A130882(1) = 0, hence a(1) = 0.
For n = 3 we have A179620(3)/A130882(3)= 7 / 7 = 1; hence a(3) = 1.
For n = 24 we have A179620(24)/A130882(24)= 34 / 17 = 2; hence a(24) = 2.
		

Crossrefs

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