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 1-5 of 5 results.

A152888 Partial sums of length of terms in A081368 where A081368(1) is set to 0.

Original entry on oeis.org

0, 2, 5, 9, 14, 21, 28, 36, 45, 55, 66, 77, 90, 104, 119, 135, 152, 170
Offset: 1

Views

Author

Roger L. Bagula, Dec 14 2008

Keywords

Comments

Previous name was: The sequence of powers necessary to reconstruct Exp[0] from Thanh Diep's sequence A081368: E=Sum[A081368[n]/10^a(n),{n,1,Length}].

References

  • C. Pickover, Mazes for the Mind, St. Martin's Press, NY, 1992, p. 350-351.

Programs

  • Mathematica
    a = {2, 71, 828, 1828, 45904, 5235360, 2874713, 52662497, 757247093, 6999595749, 66967627724, 76630353547, 5945713821785, 25166427427466, 391932003059921, 8174135966290435, 72900334295260595, 630738132328627943};
    b = Table[Length[IntegerDigits[a[[n]]]], {n, 1, Length[a]}];
    c = Table[Sum[b[[m]], {m, 1, n}] - 1, {n, 1, Length[b]}] Sum[a[[n]]/10^(c[[n]]), {n, 1, Length[a]}];
    N[% - E, 100]
  • PARI
    v=[71, 828, 1828, 45904, 5235360, 2874713, 52662497, 757247093, 6999595749, 66967627724, 76630353547, 5945713821785, 25166427427466, 391932003059921, 8174135966290435, 72900334295260595, 630738132328627943];
    concat([0],vector(#v,n,sum(j=1,n,#digits(v[j])))) \\ Joerg Arndt, Aug 13 2013

Extensions

Edited by Joerg Arndt and Michel Marcus, Aug 13 2013

A090897 Next n digits of Pi.

Original entry on oeis.org

3, 14, 159, 2653, 58979, 323846, 2643383, 27950288, 419716939, 9375105820, 97494459230, 781640628620, 8998628034825, 34211706798214, 808651328230664, 7093844609550582, 23172535940812848, 111745028410270193, 8521105559644622948, 95493038196442881097
Offset: 1

Views

Author

Michael Joseph Halm, Feb 26 2004

Keywords

Comments

More precisely: the integer resulting from reading the "next n digits of Pi" in base 10, so leading zeros cannot be directly seen, but easily be "reconstructed" from the fact that the term will have less than n digits although it is made from n digits of Pi. - M. F. Hasler, Jan 06 2023
It seems that all terms have at least one prime factor that does not appear in the combined list of prime factors of the preceding terms of the sequence. - Mario Cortés, Aug 20 2020 [Checked up to n=65. - Michel Marcus, Aug 21 2020]

Examples

			a(3) = 159 because after the first (a(1) = 3) and the next two digits of Pi (a(2) = 14) the next three are 159.
From _Aaron T Cowan_, Jan 03 2023: (Start)
Other examples are as follows and fall into a triangular digit pattern, though there is no guarantee that they will remain triangular in all cases
  a(1) = 3;
  a(2) = 14;
  a(3) = 159;
  a(4) = 2653;
  a(5) = 58979;
   (End)
Indeed, precisely whenever A086639(n) = 0, then the corresponding term of this sequence will lack one or more leading zeros and therefore the above list will deviate from the triangular shape. - _M. F. Hasler_, Jan 06 2023
		

Crossrefs

Programs

  • Maple
    Partitioner := proc(cons, len) local i, R, spl; R := []; i:=0;
    spl := L -> [seq([seq(L[i], i=1 + n*(n+1)/2..(n+1)*(n+2)/2)], n=0..len)]:
    ListTools:-Reverse(convert(floor(cons*10^((len+1)*(len+2)/2)), base, 10)):
    map(`@`(parse, cat, op), spl(%)) end:
    aList := -> Partitioner(Pi, 20); aList(20); # Peter Luschny, Aug 22 2020
  • Mathematica
    With[{pi=RealDigits[Pi,10,500][[1]]},FromDigits/@Table[Take[pi,{n (n-1)/2+1, (n(n+1))/2}],{n,25}]] (* Harvey P. Dale, Dec 24 2011 *)
  • PARI
    lista(nn) = {my(nd = 5+nn*(nn+1)/2); default(realprecision, nd); my(vd = digits(floor(Pi*10^nd))); my(pos = 1); my(vr = vector(nn)); for (n=1, nn, vr[n] = fromdigits(vector(n, k, vd[k+ pos-1])); pos += n;); vr;} \\ Michel Marcus, Aug 21 2020

Formula

a(n) = floor( Pi * 10^(n*(n+1)/2-1) ) mod (10^n). - Carl R. White, Aug 13 2010

A093473 a(n) = the next n digits of phi, the golden ratio.

Original entry on oeis.org

1, 61, 803, 3988, 74989, 484820, 4586834, 36563811, 772030917, 9805762862, 13544862270, 526046281890, 2449707207204, 18939113748475, 408807538689175, 2126633862223536, 93179318006076672, 635443338908659593
Offset: 1

Views

Author

Michael Joseph Halm, May 13 2004

Keywords

Crossrefs

Programs

  • Mathematica
    With[{phi=RealDigits[GoldenRatio,10,500][[1]]},FromDigits/@Table[Take[ phi,{n (n-1)/2+1,(n(n+1))/2}],{n,25}]] (* Harvey P. Dale, Dec 24 2011 *)
  • PARI
    { default(realprecision, 20180); x = (1 + sqrt(5))/2; for (n=1, 200, d=floor(x); x=(x-d)*10^(n+1); write("b093473.txt", n, " ", d)); } \\ Harry J. Smith, Jun 19 2009

A136517 a(0) = 3; for n > 0, break up decimal expansion of Pi into chunks of increasing lengths; leading zeros are not printed.

Original entry on oeis.org

3, 1, 41, 592, 6535, 89793, 238462, 6433832, 79502884, 197169399, 3751058209, 74944592307, 816406286208, 9986280348253, 42117067982148, 86513282306647, 938446095505822, 31725359408128481, 117450284102701938, 5211055596446229489
Offset: 0

Views

Author

N. J. A. Sloane, Apr 21 2008

Keywords

References

  • Sylvia Nasar, A Beautiful Mind (1998), p. 210.
  • Clifford A. Pickover, A Passion for Mathematics, Wiley, 2005; see p. 64.

Crossrefs

Programs

  • Maple
    with(StringTools): lim:=23: s:=convert(evalf[lim^2](Pi-3),string): printf("3, "): for n from 1 to lim do printf("%d, ",parse(SubString(s,(n-1)*n/2+2..n*(n+1)/2+1))); od: # Nathaniel Johnston, May 08 2011
  • Mathematica
    Join[{3},FromDigits/@With[{p=RealDigits[Pi,10,220][[1]]},Table[ Take[ p, {(n(n-1))/2+2,(n(n-1))/2+1+n}],{n,20}]]] (* Harvey P. Dale, Aug 20 2011 *)

Extensions

Extended by Nathaniel Johnston, May 08 2011

A267325 Next n digits of sqrt(2).

Original entry on oeis.org

1, 41, 421, 3562, 37309, 504880, 1688724, 20969807, 856967187, 5376948073, 17667973799, 73247846210, 7038850387534, 32764157273501, 384623091229702, 4924836055850737, 21264412149709993, 583141322266592750, 5592755799950501152, 78206057147010955997
Offset: 1

Views

Author

Ilya Gutkovskiy, Jan 13 2016

Keywords

Examples

			a(2) = 41 because the second and third digits of sqrt(2) are 4 and 1.
		

Crossrefs

Programs

  • Magma
    [Floor(Sqrt(2)*10^(n*(n + 1)/2 - 1)) mod (10^n): n in [1..30]]; // Vincenzo Librandi, Feb 15 2016
    
  • Mathematica
    Table[Mod[Floor[Sqrt[2] 10^(n ((n + 1)/2) - 1)], 10^n], {n, 1, 20}]
    Table[Floor[10^(-1 + (n (1 + n))/2) Sqrt[2]] + Ceiling[-(Floor[10^(-1 + (n (1 + n))/2) Sqrt[2]]/10^n)] 10^n, {n, 1, 20}]
    With[{x=20},FromDigits/@TakeList[RealDigits[Sqrt[2],10,(x(x+1))/2] [[1]], Range[x]]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, May 04 2019 *)
  • PARI
    a(n) = lift(Mod(floor(sqrt(2)*10^(n*(n + 1)/2 - 1)), 10^n)); \\ G. C. Greubel, Oct 07 2018

Formula

a(n) = floor(sqrt(2)*10^(n*(n + 1)/2 - 1)) mod (10^n).
Showing 1-5 of 5 results.