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 30 results. Next

A328213 Numbers m such that m and m+1 are consecutive lazy-Fibonacci-Niven numbers (A328212).

Original entry on oeis.org

1, 15, 35, 369, 549, 710, 890, 1089, 1989, 2196, 2629, 2951, 3311, 3679, 3684, 4927, 5268, 5291, 5488, 5603, 5775, 5819, 5928, 5940, 6524, 7072, 7364, 7403, 7475, 7500, 7657, 7812, 8567, 9254, 9360, 9372, 9383, 9477, 9841, 10205, 10304, 10360, 11816, 13299, 13454
Offset: 1

Views

Author

Amiram Eldar, Oct 07 2019

Keywords

Examples

			15 is in the sequence since both 15 and 16 are in A328212: A112310(15) = 3 is a divisor of 15, and A112310(16) = 4 is a divisor of 16.
		

Crossrefs

Programs

  • Mathematica
    ooQ[n_] := Module[{k = n}, While[k > 3, If[Divisible[k, 4], Return[True], k = Quotient[k, 2]]]; False]; c = 0; cn = 0; k = 1; s = {}; v = Table[-1, {2}]; While[cn < 45, If[! ooQ[k], c++; d = Total@IntegerDigits[k, 2]; If[Divisible[c, d], v = Join[Rest[v], {c}]; If[AllTrue[Differences[v], # == 1 &], cn++; AppendTo[s, c - 1]]]]; k++]; s

A328214 Starts of runs of 3 consecutive lazy-Fibonacci-Niven numbers (A328212).

Original entry on oeis.org

27312, 37504, 48060, 83248, 198254, 269856, 319694, 386136, 423520, 434300, 518175, 525672, 539800, 572184, 690858, 701118, 793799, 886534, 998866, 1015035, 1258444, 1396582, 1409058, 1511600, 1557422, 1680378, 1729398, 1753818, 2044768, 2136263, 2310624, 2396438, 2421024
Offset: 1

Views

Author

Amiram Eldar, Oct 07 2019

Keywords

Examples

			27312 is in the sequence since 27312, 27313 and 27314 are in A328212: A112310(27312) = 16 is a divisor of 27312, A112310(27312) = 13 is a divisor of 27313, and A112310(27314) = 14 is a divisor of 27314.
		

Crossrefs

Programs

  • Mathematica
    ooQ[n_] := Module[{k = n}, While[k > 3, If[Divisible[k, 4], Return[True], k = Quotient[k, 2]]]; False]; c = 0; cn = 0; k = 1; s = {}; v = Table[-1, {3}]; While[cn < 33, If[! ooQ[k], c++; d = Total@IntegerDigits[k, 2]; If[Divisible[c, d], v = Join[Rest[v], {c}]; If[AllTrue[Differences[v], # == 1 &], cn++; AppendTo[s, c - 2]]]]; k++]; s

A328215 Starts of runs of 4 consecutive lazy-Fibonacci-Niven numbers (A328212).

Original entry on oeis.org

3674769, 17434975, 22711023, 26152125, 32784723, 41221725, 57846123, 93416568, 101681916, 122873490, 173504940, 225947148, 234209247, 259557450, 333681684, 377858544, 396241410, 413770056, 432640989, 443496447, 444571650, 484381323, 497625360, 556123167, 564869940
Offset: 1

Views

Author

Amiram Eldar, Oct 07 2019

Keywords

Comments

Grundman found a(1) and proved that there are no runs of 5 consecutive lazy-Fibonacci-Niven numbers.

Examples

			3674769 is in the sequence since 3674769, 3674770, 3674771 and 3674772 are in A328212: A112310(3674769) = 21 is a divisor of 3674769, A112310(3674770) = 22 is a divisor of 3674770, A112310(3674771) = 17 is a divisor of 3674771, and A112310(3674772) = 18 is a divisor of 3674772.
		

Crossrefs

Programs

  • Mathematica
    ooQ[n_] := Module[{k = n}, While[k > 3, If[Divisible[k, 4], Return[True], k = Quotient[k, 2]]]; False]; c = 0; cn = 0; k = 1; s = {}; v = Table[-1, {4}]; While[cn < 10, If[! ooQ[k], c++; d = Total@IntegerDigits[k, 2]; If[Divisible[c, d], v = Join[Rest[v], {c}]; If[AllTrue[Differences[v], # == 1 &], cn++; AppendTo[s, c - 3]]]]; k++]; s

Extensions

More terms from Amiram Eldar, Oct 23 2019

A330711 Numbers that are both Zeckendorf-Niven numbers (A328208) and lazy-Fibonacci-Niven numbers (A328212).

Original entry on oeis.org

1, 2, 4, 6, 12, 16, 30, 36, 48, 55, 60, 72, 78, 84, 90, 102, 105, 126, 144, 156, 168, 180, 184, 192, 208, 238, 240, 252, 264, 304, 315, 320, 322, 344, 360, 370, 378, 396, 430, 432, 488, 528, 536, 540, 576, 590, 605, 609, 621, 639, 648, 657, 660, 672, 680, 702
Offset: 1

Views

Author

Amiram Eldar, Dec 27 2019

Keywords

Examples

			6 is in the sequence since A007895(6) = 2 and A112310(6) = 3, and both 2 and 3 are divisors of 6.
		

Crossrefs

Intersection of A328208 and A328212.

Programs

  • Mathematica
    zeckSum[n_] := Length[DeleteCases[NestWhileList[# - Fibonacci[Floor[Log[Sqrt[5]*# + 3/2]/Log[GoldenRatio]]] &, n, # > 1 &], 0]];
    fibTerms[n_] := Module[{k = Ceiling[Log[GoldenRatio, n*Sqrt[5]]], t = n, fr = {}}, While[k > 1, If[t >= Fibonacci[k], AppendTo[fr, 1]; t = t - Fibonacci[k], AppendTo[fr, 0]]; k--]; fr];
    dualZeckSum[n_] := Module[{v = fibTerms[n]}, nv = Length[v]; i = 1; While[i <= nv - 2, If[v[[i]] == 1 && v[[i + 1]] == 0 && v[[i + 2]] == 0, v[[i]] = 0; v[[i + 1]] = 1; v[[i + 2]] = 1; If[i > 2, i -= 3]]; i++]; i = Position[v, _?(# > 0 &)]; If[i == {}, 0, Total[v[[i[[1, 1]] ;; -1]]]]];
    Select[Range[1000], Divisible[#, zeckSum[#]] && Divisible[#, dualZeckSum[#]] &]

A330713 Numbers k such that both k and k+1 are Zeckendorf-Niven numbers (A328208) and lazy-Fibonacci-Niven numbers (A328212).

Original entry on oeis.org

1, 7475, 10205, 13740, 40754, 52479, 93044, 95984, 141911, 151487, 196416, 198255, 202824, 202895, 213920, 231552, 335535, 339744, 363320, 366876, 404719, 408680, 434259, 446480, 487710, 495159, 504440, 528408, 585599, 607410, 645560, 646575, 665567, 735020, 736280
Offset: 1

Views

Author

Amiram Eldar, Dec 27 2019

Keywords

Comments

Can 3 consecutive numbers be both Zeckendorf-Niven numbers and lazy-Fibonacci-Niven numbers? Equivalently, are there numbers that are both in A328210 and A328214?

Examples

			7475 is a term since A007895(7475) = 5 and A112310(7475) = 13 and both 5 and 13 are divisors of 7475, and A007895(7476) = 6 and A112310(7476) = 12 and both 6 and 12 are divisors of 7476.
		

Crossrefs

Intersection of A328209 and A328213.

A333426 Primorial base Niven numbers: numbers divisible by their sum of digits in primorial base (A276150).

Original entry on oeis.org

1, 2, 4, 6, 8, 9, 12, 16, 18, 20, 24, 25, 30, 32, 33, 36, 40, 42, 44, 45, 48, 50, 60, 64, 65, 66, 68, 70, 72, 77, 84, 88, 90, 92, 96, 105, 108, 112, 117, 120, 132, 133, 136, 144, 150, 154, 156, 160, 168, 180, 182, 184, 189, 192, 198, 200, 210, 212, 213, 216, 220
Offset: 1

Views

Author

Amiram Eldar, Mar 20 2020

Keywords

Comments

Numbers k for which A276086(k) is in A373852. - Antti Karttunen, Jun 22 2024

Examples

			1 is a term since A276150(1) = 1 divides 1;
2 is a term since A276150(2) = 1 divides 2;
		

Crossrefs

Programs

  • Mathematica
    max = 5; bases = Prime @ Range[max, 1, -1]; nmax = Times @@ bases - 1; sumdig[n_] := Plus @@ IntegerDigits[n, MixedRadix[bases]]; Select[Range[nmax], Divisible[#, sumdig[#]] &]
  • PARI
    isA333426 = A373834; \\ Antti Karttunen, Jun 22 2024

A331728 Negabinary-Niven numbers: numbers divisible by the sum of digits in their negabinary representation (A027615).

Original entry on oeis.org

1, 2, 3, 4, 6, 8, 9, 12, 14, 15, 16, 18, 20, 21, 24, 28, 30, 32, 33, 35, 36, 40, 42, 48, 50, 52, 54, 56, 57, 60, 62, 63, 64, 66, 68, 69, 72, 76, 78, 80, 81, 84, 88, 90, 91, 95, 96, 100, 102, 108, 110, 112, 114, 120, 124, 125, 126, 128, 129, 132, 136, 138, 140
Offset: 1

Views

Author

Amiram Eldar, Jan 27 2020

Keywords

Examples

			6 is a term since A039724(6) = 11010 and 1 + 1 + 0 + 1 + 0 = 3 is a divisor of 6.
		

Crossrefs

Programs

  • Mathematica
    negaBinWt[n_] := negaBinWt[n] = If[n==0, 0, negaBinWt[Quotient[n-1, -2]] + Mod[n, 2]]; negaBinNivenQ[n_] := Divisible[n, negaBinWt[n]]; Select[Range[100], negaBinNivenQ]

A331085 Positive negaFibonacci-Niven numbers: positive numbers divisible by the number of terms in their negaFibonacci representation (A331083).

Original entry on oeis.org

1, 2, 4, 5, 6, 9, 10, 12, 13, 14, 18, 24, 26, 27, 30, 34, 36, 48, 55, 60, 64, 68, 69, 72, 78, 84, 86, 87, 88, 89, 90, 93, 94, 96, 99, 100, 102, 108, 110, 112, 116, 120, 140, 144, 150, 155, 156, 160, 172, 176, 177, 178, 180, 183, 184, 188, 192, 195, 196, 200, 204
Offset: 1

Views

Author

Amiram Eldar, Jan 08 2020

Keywords

Comments

The k-th Fibonacci number is a term for all odd k, since its negaFibonacci representation is 1 followed by (k-1) zeros.

Examples

			4 is a term since the negaFibonacci representation of 4 is 10010 whose sum of digits is 1 + 0 + 0 + 1 + 0 = 2 which is a divisor of 4.
		

Crossrefs

Programs

  • Mathematica
    ind[n_] := Floor[Log[Abs[n]*Sqrt[5] + 1/2]/Log[GoldenRatio]]; f[1] = 1; f[n_] := If[n > 0, i = ind[n - 1]; If[EvenQ[i], i++]; i, i = ind[-n]; If[OddQ[i], i++]; i]; negaFibTermsNum[n_] := Module[{k = n, s = 0}, While[k != 0, i = f[k]; s += 1; k -= Fibonacci[-i]]; s]; Select[Range[200], Divisible[#, negaFibTermsNum[#]] &]

A334308 Base phi Niven numbers: numbers divisible by the number of 1's in their base phi representation (A055778).

Original entry on oeis.org

1, 2, 6, 12, 15, 16, 18, 20, 30, 35, 36, 45, 48, 55, 60, 70, 72, 78, 84, 90, 91, 95, 96, 98, 104, 108, 132, 144, 147, 154, 168, 175, 184, 189, 208, 224, 231, 232, 245, 252, 256, 261, 264, 270, 275, 280, 282, 287, 294, 315, 322, 324, 330, 336, 340, 342, 351, 357
Offset: 1

Views

Author

Amiram Eldar, Apr 22 2020

Keywords

Examples

			6 is a term since its base phi representation is 1010.0001, and the number of 1's is 3, which is a divisor of 6.
		

Crossrefs

Programs

  • Mathematica
    phiDigSum[1] = 1; phiDigSum[n_] := Plus @@ RealDigits[n, GoldenRatio, 2*Ceiling[ Log[GoldenRatio, n]] ][[1]]; Select[Range[360], Divisible[#, phiDigSum[#]] &]

A342426 Niven numbers in base 3/2: numbers divisible by their sum of digits in fractional base 3/2 (A244040).

Original entry on oeis.org

1, 2, 6, 9, 14, 21, 40, 42, 56, 72, 84, 108, 110, 120, 126, 130, 143, 154, 156, 162, 165, 168, 169, 176, 180, 182, 189, 198, 220, 225, 231, 243, 252, 280, 288, 297, 306, 308, 320, 322, 330, 336, 348, 350, 364, 390, 423, 430, 432, 459, 460, 462, 480, 490, 504
Offset: 1

Views

Author

Amiram Eldar, Mar 11 2021

Keywords

Examples

			6 is a term since its representation in base 3/2 is 210 and 2 + 1 + 0 = 3 is a divisor of 6.
9 is a term since its representation in base 3/2 is 2100 and 2 + 1 + 0 + 0 = 3 is a divisor of 9.
		

Crossrefs

Subsequences: A342427, A342428, A342429.
Similar sequences: A005349 (decimal), A049445 (binary), A064150 (ternary), A064438 (quaternary), A064481 (base 5), A118363 (factorial), A328208 (Zeckendorf), A328212 (lazy Fibonacci), A331085 (negaFibonacci), A333426 (primorial), A334308 (base phi), A331728 (negabinary).

Programs

  • Mathematica
    s[0] = 0; s[n_] := s[n] = s[2*Floor[n/3]] + Mod[n, 3]; q[n_] := Divisible[n, s[n]]; Select[Range[500], q]
Showing 1-10 of 30 results. Next