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 42 results. Next

A135076 Primes appearing in A001370.

Original entry on oeis.org

2, 7, 5, 11, 13, 7, 19, 19, 29, 31, 41, 37, 29, 43, 41, 37, 47, 61, 59, 67, 71, 61, 73, 79, 89, 109, 103, 89, 109, 107, 107, 113, 139, 151, 127, 137, 107, 113, 167, 173, 167, 181, 191, 173, 193, 223, 233, 211, 199, 229, 251, 239, 281, 251, 277, 281, 239, 241, 239, 269
Offset: 1

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Author

Zak Seidov, Nov 18 2007

Keywords

Examples

			a(1)=2 because with s=A076203(1)=1, 2^s=2 and sod(2)=2; sod(x)=sum of digits of x;
a(2)=7 because with s=A076203(2)=4, 2^s=16 and sod(16)=7.
a(7)=9 because with s=A076203(7)=12, 2^s=4096 and sod(4096)=19.
a(8)=9 because with s=A076203(8)=18, 2^s=262144 and sod(262144)=19.
		

Crossrefs

Programs

  • PARI
    lista(nn) = {for (n=1, nn, sd = sumdigits(2^n); if (isprime(sd), print1(sd, ", ")););} \\ Michel Marcus, Oct 13 2013

Formula

a(n)=A007953(2^A076203(n)).

Extensions

Name corrected by Michel Marcus, Oct 13 2013

A004207 a(0) = 1, a(n) = sum of digits of all previous terms.

Original entry on oeis.org

1, 1, 2, 4, 8, 16, 23, 28, 38, 49, 62, 70, 77, 91, 101, 103, 107, 115, 122, 127, 137, 148, 161, 169, 185, 199, 218, 229, 242, 250, 257, 271, 281, 292, 305, 313, 320, 325, 335, 346, 359, 376, 392, 406, 416, 427, 440, 448, 464, 478, 497, 517, 530, 538
Offset: 0

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Author

Keywords

Comments

If the leading 1 is omitted, this is the important sequence b(1)=1, for n >= 2, b(n) = b(n-1) + sum of digits of b(n-1). Cf. A016052, A016096, etc. - N. J. A. Sloane, Dec 01 2013
Same digital roots as A065075 (Sum of digits of the sum of the preceding numbers) and A001370 (Sum of digits of 2^n); they end in the cycle {1 2 4 8 7 5}. - Alexandre Wajnberg, Dec 11 2005
More precisely, mod 9 this sequence is 1 (1 2 4 8 7 5)*, the parenthesized part being repeated indefinitely. This shows that this sequence is disjoint from A016052. - N. J. A. Sloane, Oct 15 2013
There are infinitely many even terms (Belov 2003).
a(n) = A007618(n-5) for n > 57; a(n) = A006507(n-4) for n > 15. - Reinhard Zumkeller, Oct 14 2013

References

  • N. Agronomof, Problem 4421, L'Intermédiaire des mathématiciens, v. 21 (1914), p. 147.
  • D. R. Kaprekar, Puzzles of the Self-Numbers. 311 Devlali Camp, Devlali, India, 1959.
  • D. R. Kaprekar, The Mathematics of the New Self Numbers, Privately printed, 311 Devlali Camp, Devlali, India, 1963.
  • J. Roberts, Lure of the Integers, Math. Assoc. America, 1992, p. 65.
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
  • G. E. Stevens and L. G. Hunsberger, A Result and a Conjecture on Digit Sum Sequences, J. Recreational Math. 27, no. 4 (1995), pp. 285-288.
  • James J. Tattersall, Elementary Number Theory in Nine Chapters, Cambridge University Press, 1999, page 37.

Crossrefs

For the base-2 analog see A010062.
A065075 gives sum of digits of a(n).
See A219675 for an essentially identical sequence.

Programs

  • Haskell
    a004207 n = a004207_list !! n
    a004207_list = 1 : iterate a062028 1
    -- Reinhard Zumkeller, Oct 14 2013, Sep 12 2011
    
  • Maple
    read("transforms") :
    A004207 := proc(n)
        option remember;
        if n = 0 then
            1;
        else
            add( digsum(procname(i)),i=0..n-1) ;
        end if;
    end proc: # R. J. Mathar, Apr 02 2014
    # second Maple program:
    a:= proc(n) option remember; `if`(n<2, 1, (t->
         t+add(i, i=convert(t, base, 10)))(a(n-1)))
        end:
    seq(a(n), n=0..60);  # Alois P. Heinz, Jul 31 2022
  • Mathematica
    f[s_] := Append[s, Plus @@ Flatten[IntegerDigits /@ s]]; Nest[f, {1}, 55] (* Robert G. Wilson v, May 26 2006 *)
    f[n_] := n + Plus @@ IntegerDigits@n; Join[{1}, NestList[f, 1, 80]] (* Alonso del Arte, May 27 2006 *)
  • PARI
    a(n) = { my(f(d, i) = d+vecsum(digits(d)), S=vector(n)); S[1]=1; for(k=1, n-1, S[k+1] = fold(f, S[1..k])); S } \\ Satish Bysany, Mar 03 2017
    
  • PARI
    a = 1; print1(a, ", "); for(i = 1, 50, print1(a, ", "); a = a + sumdigits(a)); \\ Nile Nepenthe Wynar, Feb 10 2018
    
  • Python
    from itertools import islice
    def agen():
        yield 1; an = 1
        while True: yield an; an += sum(map(int, str(an)))
    print(list(islice(agen(), 54))) # Michael S. Branicky, Jul 31 2022

Formula

For n>1, a(n) = a(n-1) + sum of digits of a(n-1).
For n > 1: a(n) = A062028(a(n-1)). - Reinhard Zumkeller, Oct 14 2013

Extensions

Errors from 25th term on corrected by Leonid Broukhis, Mar 15 1996
Typo in definition fixed by Reinhard Zumkeller, Sep 14 2011

A004166 Sum of digits of 3^n.

Original entry on oeis.org

1, 3, 9, 9, 9, 9, 18, 18, 18, 27, 27, 27, 18, 27, 45, 36, 27, 27, 45, 36, 45, 27, 45, 54, 54, 63, 63, 81, 72, 72, 63, 81, 63, 72, 99, 81, 81, 90, 90, 81, 90, 99, 90, 108, 90, 99, 108, 126, 117, 108, 144, 117, 117, 135, 108, 90, 90, 108, 126, 117, 99
Offset: 0

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Author

Keywords

Comments

All terms a(n), n > 1, are divisible by 9. - M. F. Hasler, Sep 27 2017

Crossrefs

Cf. sum of digits of k^n: A001370 (k=2), this sequence (k=3), A065713 (k=4), A066001 (k=5), A066002 (k=6), A066003 (k=7), A066004 (k=8), A065999 (k=9), A066005 (k=11), A066006 (k=12), A175527 (k=13).

Programs

  • Mathematica
    Total[IntegerDigits[#]]&/@(3^Range[0,60]) (* Harvey P. Dale, Mar 03 2013 *)
    Table[Total[IntegerDigits[3^n]], {n, 0, 60}] (* Vincenzo Librandi, Oct 08 2013 *)
  • PARI
    a(n)=sumdigits(3^n); \\ Michel Marcus, Nov 01 2013
    
  • Python
    def a(n): return sum(map(int, str(3**n)))
    print([a(n) for n in range(61)]) # Michael S. Branicky, Apr 25 2022

Formula

a(n) = A007953(A000244(n)). - Michel Marcus, Nov 01 2013

Extensions

Edited by M. F. Hasler, May 18 2017

A066001 Sum of digits of 5^n.

Original entry on oeis.org

1, 5, 7, 8, 13, 11, 19, 23, 25, 26, 40, 38, 28, 23, 34, 44, 58, 56, 64, 59, 61, 62, 67, 74, 82, 77, 79, 89, 85, 83, 91, 104, 106, 89, 103, 92, 109, 104, 124, 134, 130, 137, 145, 149, 151, 116, 112, 128, 145, 158, 151, 152, 130, 119, 127, 167, 196, 215, 211, 191
Offset: 0

Views

Author

N. J. A. Sloane, Dec 11 2001

Keywords

Comments

We can expect and conjecture that a(n) ~ 4.5*log_10(5)*n, but for n ~ 10^3..10^4 there are still fluctuations of +- 1%, e.g., a(10^3)/log_10(5) ~ 4538, a(10^4)/log_10(5) ~ 44518. Modulo 9, the sequence is periodic with period (1, 5, 7, 8, 4, 2) of length 6. No term is divisible by 3, a(n) = (-1)^n (mod 3). - M. F. Hasler, May 18 2017

Crossrefs

Cf. sum of digits of k^n: A001370 (k=2), A004166 (k=3), A065713 (k=4), this sequence (k=5), A066002 (k=6), A066003 (k=7), A066004 (k=8), A065999 (k=9), A066005 (k=11), A066006 (k=12), A175527 (k=13).

Programs

Formula

a(n) = A007953(A000351(n)). - Michel Marcus, Aug 05 2025

A065075 Sum of digits of the sum of the preceding numbers.

Original entry on oeis.org

1, 1, 2, 4, 8, 7, 5, 10, 11, 13, 8, 7, 14, 10, 2, 4, 8, 7, 5, 10, 11, 13, 8, 16, 14, 19, 11, 13, 8, 7, 14, 10, 11, 13, 8, 7, 5, 10, 11, 13, 17, 16, 14, 10, 11, 13, 8, 16, 14, 19, 20, 13, 8, 16, 14, 19, 20, 13, 8, 16, 14, 19, 20, 22, 17, 16, 14, 19, 20, 13, 17, 16, 14, 19, 20, 13
Offset: 1

Views

Author

Bodo Zinser, Nov 09 2001

Keywords

Comments

This sequence has the same digital roots as A004207 (a(1) = 1, a(n) = sum of digits of all previous terms) and A001370 (Sum of digits of 2^n); the digital roots sequence ends in the cycle {1 2 4 8 7 5}. - Alexandre Wajnberg, Dec 11 2005
The missing digital roots are precisely the multiples of 3. - Alexandre Wajnberg, Dec 28 2005
Conjecture: every non-multiple of 3 does appear in the sequence. - Franklin T. Adams-Watters, Jun 29 2009. See A230289. - N. J. A. Sloane, Oct 17 2013
a(n) = sum of digits of A004207(n). - N. J. A. Sloane, Oct 18 2013

Examples

			a(6) = 7 because a(1)+a(2)+a(3)+a(4)+a(5) = 16 and 7 = 1+6.
		

Crossrefs

Programs

  • Haskell
    a065075 n = a065075_list !! (n-1)
    a065075_list = 1 : 1 : f 2 where
       f x = y : f (x + y) where y = a007953 x
    -- Reinhard Zumkeller, Nov 13 2014
  • Maple
    read transforms;
    sp:=1;
    lprint(1,sp);
    s:=sp;
    for n from 2 to 10000 do
    sp:=digsum(s);
    lprint(n,sp);
    s:=s+sp;
    od:
    # N. J. A. Sloane, Oct 17 2013
  • PARI
    a065075(m) = local(a,j,s); a=1; print1(a,", "); s=a; for(j=1,m,a=sumdigits(s); print1(a,", "); s=s+a)
    a065075(80)
    

Formula

a(1) = 1, a(2) = 1, a(n) = sum of digits of (a(1)+a(2)+...+a(n-1)).

Extensions

More terms from Larry Reeves (larryr(AT)acm.org) and Klaus Brockhaus, Nov 13 2001
Edited by Franklin T. Adams-Watters, Jun 29 2009

A066002 Sum of digits of 6^n.

Original entry on oeis.org

1, 6, 9, 9, 18, 27, 27, 36, 36, 36, 36, 45, 45, 36, 54, 63, 54, 72, 72, 63, 72, 81, 63, 72, 90, 90, 99, 99, 90, 135, 117, 99, 126, 126, 135, 135, 126, 135, 135, 162, 171, 126, 153, 153, 153, 162, 180, 162, 153, 162, 171, 216, 171, 216, 171, 162
Offset: 0

Views

Author

N. J. A. Sloane, Dec 11 2001

Keywords

Crossrefs

Cf. sum of digits of k^n: A001370 (k=2), A004166 (k=3), A065713 (k=4), A066001 (k=5), this sequence (k=6), A066003(k=7), A066004 (k=8), A065999 (k=9), A066005 (k=11), A066006 (k=12), A175527 (k=13).
Cf. A007953.

Programs

  • Mathematica
    Table[Total[IntegerDigits[6^n]], {n, 0, 60}] (* Vincenzo Librandi, Oct 08 2013 *)
  • PARI
    a(n) = sumdigits(6^n); \\ Michel Marcus, Nov 01 2013

Formula

a(n) = A007953(A000400(n)). - Michel Marcus, Nov 01 2013 [corrected by Georg Fischer, Dec 28 2020]

A066003 Sum of digits of 7^n.

Original entry on oeis.org

1, 7, 13, 10, 7, 22, 28, 25, 31, 28, 43, 49, 37, 52, 58, 64, 52, 58, 73, 79, 76, 82, 97, 85, 73, 97, 112, 91, 133, 121, 118, 115, 103, 127, 142, 157, 136, 115, 130, 136, 142, 148, 136, 169, 175, 163, 187, 175, 136, 178, 184, 217, 196, 220, 217
Offset: 0

Views

Author

N. J. A. Sloane, Dec 11 2001

Keywords

Crossrefs

Cf. A000420 (7^n), A007953 (sum of digits).
Cf. sum of digits of k^n: A001370 (k=2), A004166 (k=3), A065713 (k=4), A066001 (k=5), A066002 (k=6), this sequence (k=7), A066004 (k=8), A065999 (k=9), A066005 (k=11), A066006 (k=12), A175527 (k=13).

Programs

  • Magma
    [ &+Intseq(7^n): n in [0..60] ];
    
  • Mathematica
    Table[Total[IntegerDigits[7^n]],{n,55}] (* Harvey P. Dale, Nov 22 2010 *)
  • PARI
    a(n) = sumdigits(7^n); \\ Michel Marcus, Nov 01 2013

Formula

a(n) = A007953(A000420(n)). - Michel Marcus, Nov 01 2013

A175527 Digit sum of 13^n.

Original entry on oeis.org

1, 4, 16, 19, 22, 25, 37, 40, 34, 46, 67, 52, 55, 58, 97, 73, 85, 88, 91, 85, 115, 91, 121, 106, 109, 121, 133, 118, 121, 133, 163, 184, 169, 181, 193, 169, 172, 175, 178, 199, 193, 214, 226, 238, 169, 190, 247, 241, 208, 247, 232, 253, 292, 241, 316, 292, 268, 271, 301, 286, 298, 337, 304, 325
Offset: 0

Views

Author

N. J. A. Sloane, Dec 03 2010

Keywords

Comments

It is surprising that many values repeat twice (for 85, 91, 121, 133, 169 this happens at a(n) = a(n+3) (but 169 occurs later for a third time), for 193, 241, 292, ... the second occurrence comes later) while many other values never occur. Is there a simple explanation? - M. F. Hasler, May 18 2017

Crossrefs

Cf. sum of digits of k^n: A001370 (k=2), A004166 (k=3), A065713 (k=4), A066001 (k=5), A066002 (k=6), A066003 (k=7), A066004 (k=8), A065999 (k=9), A066005 (k=11), A066006 (k=12), this sequence (k=13).

Programs

  • Mathematica
    Table[Total[IntegerDigits[13^k]], {k,0,1000}]
  • PARI
    a(n)=sumdigits(13^n); \\ Michel Marcus, Nov 01 2013

Formula

a(n) = A007953(A001022(n)). - Michel Marcus, Nov 01 2013
a(n) ~ 4.5*log_10(13)*n ~ 5.0127*n (conjectured). - M. F. Hasler, May 18 2017

A002114 Glaisher's H' numbers.

Original entry on oeis.org

1, 11, 301, 15371, 1261501, 151846331, 25201039501, 5515342166891, 1538993024478301, 533289474412481051, 224671379367784281901, 113091403397683832932811, 67032545884354589043714301, 46211522130188693681603906171
Offset: 1

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Author

Keywords

Comments

a(n) mod 9 = 1,2,4,8,7,5 repeated period 6 (A153130, see also A001370). a(n) mod 10 = 1. - Paul Curtz, Sep 10 2009

References

  • A. Fletcher, J. C. P. Miller, L. Rosenhead and L. J. Comrie, An Index of Mathematical Tables. Vols. 1 and 2, 2nd ed., Blackwell, Oxford and Addison-Wesley, Reading, MA, 1962, Vol. 1, p. 76.
  • N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Programs

  • Maple
    a := n -> (-1)^n*6^(2*n)*(Zeta(0,-n*2,1/3)-Zeta(0,-n*2, 5/6)):
    seq(a(n), n=1..14);
  • Mathematica
    Select[Rest[With[{nn=28},CoefficientList[Series[1/(2 (2Cos[x]-1)), {x,0,nn}], x]Range[0,nn]!]],#!=0&] (* Harvey P. Dale, Jul 27 2011 *)
    FullSimplify[Table[(-1)^(s+1) * BernoulliB[2*s] * (Zeta[2*s + 1, 1/6] - Zeta[2*s + 1, 5/6]) / (4*Pi*Sqrt[3]*Zeta[2*s]), {s, 1, 20}]]  (* Vaclav Kotesovec, May 05 2020 *)
  • Maxima
    a(n) := sum(sum(binomial(k,j)*(-1)^(k-j+1)*1/2^(j-1)*sum((-1)^(n)*binomial(j,i)*(2*i-j)^(2*n),i,0,floor((j-1)/2)),j,0,k)*(-2)^(k-1),k,1,2*n); /* Vladimir Kruchinin, Aug 05 2010 */

Formula

H'(n) = H(n)/3, where H(n)=2^(2n+1)*I(n) (see A002112) and e.g.f. for (-1)^n*I(n) is (3/2)/(1+exp(x)+exp(-x)) (see A047788, A047789).
H'(n) = A000436(n)/2^(2n+1). - Philippe Deléham, Jan 17 2004
For n > 0, H'(n) = Sum{k = 0..n, T(n, k)*9^(n-k)*2^(k-1) }; where DELTA is the operator defined in A084938, T(n, k) is the triangle, read by rows, given by :[0, 1, 0, 4, 0, 9, 0, 16, 0, 25, ...] DELTA [1, 0, 10, 0, 28, 0, 55, 0, 90, ..]= {1}; {0, 1}; {0, 1, 1}; {0, 1, 12, 1}; {0, 1, 63, 123, 1}; {0, 1, 274, 2366, 1234, 1}; ... For 1, 10, 28, 55, 90, 136, ... see A060544 or A060544. - Philippe Deléham, Jan 17 2004
E.g.f. 1/2*1/(2*cos(x)-1). a(n)=sum(sum(binomial(k,j)*(-1)^(k-j+1)*1/2^(j-1)*sum((-1)^(n)*binomial(j,i)*(2*i-j)^(2*n),i,0,floor((j-1)/2)),j,0,k)*(-2)^(k-1),k,1,2*n), n>0. - Vladimir Kruchinin, Aug 05 2010
E.g.f.: E(x)= x^2/(G(0)-x^2) ; G(k)= 2*(2*k+1)*(k+1) - x^2 + 2*x^2*(2*k+1)*(k+1)/G(k+1); (continued fraction Euler's kind, 1-step ). - Sergei N. Gladkovskii, Jan 03 2012
If E(x)=Sum(k=0,1,..., a(k+1)*x^(2k+2)), then A002114(k) = a(k+1)*(2*k+2)!. - Sergei N. Gladkovskii, Jan 09 2012
a(n) ~ (2*n)! * 3^(2*n+1/2) / Pi^(2*n+1). - Vaclav Kotesovec, Feb 26 2014
a(n) = (-1)^n*6^(2*n)*(zeta(-n*2,1/3)-zeta(-n*2,5/6)), where zeta(a, z) is the generalized Riemann zeta function.
From Vaclav Kotesovec, May 05 2020: (Start)
a(n) = (2*n)! * (zeta(2*n+1, 1/6) - zeta(2*n+1, 5/6)) / (sqrt(3)*(2*Pi)^(2*n+1)).
a(n) = (-1)^(n+1) * Bernoulli(2*n) * (zeta(2*n+1, 1/6) - zeta(2*n+1, 5/6)) / (4*Pi*sqrt(3)*zeta(2*n)). (End)
Conjectural e.g.f.: Sum_{n >= 1} (-1)^n*Product_{k = 1..n} (1 - exp(A007310(k)*z) ) = z + 11*z^2/2! + 301*z^3/3! + .... - Peter Bala, Dec 09 2021

A065999 Sum of digits of 9^n.

Original entry on oeis.org

1, 9, 9, 18, 18, 27, 18, 45, 27, 45, 45, 45, 54, 63, 72, 63, 63, 99, 81, 90, 90, 90, 90, 108, 117, 144, 117, 108, 90, 126, 99, 153, 144, 117, 153, 144, 162, 171, 153, 153, 153, 198, 162, 171, 198, 216, 171, 198, 198, 225, 153, 252, 216, 234, 207
Offset: 0

Views

Author

N. J. A. Sloane, Dec 11 2001

Keywords

Comments

a(n) mod 9 = 0 for n > 0. - Reinhard Zumkeller, May 14 2011

Crossrefs

Cf. sum of digits of k^n: A001370 (k=2), A004166 (k=3), A065713 (k=4), A066001 (k=5), A066002 (k=6), A066003(k=7), A066004 (k=8), this sequence (k=9), A066005 (k=11), A066006 (k=12), A175527 (k=13).
Cf. also A056888, A001019.

Programs

  • Mathematica
    Table[Total[IntegerDigits[9^n]], {n, 0, 60}] (* Vincenzo Librandi, Oct 08 2013 *)
  • PARI
    a(n) = sumdigits(9^n); \\ Michel Marcus, Nov 01 2013

Formula

a(n) = A007953(A001019(n)). - Michel Marcus, Nov 01 2013
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