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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A063010 Carryless binary square of n; also Moser-de Bruijn sequence written in binary.

Original entry on oeis.org

0, 1, 100, 101, 10000, 10001, 10100, 10101, 1000000, 1000001, 1000100, 1000101, 1010000, 1010001, 1010100, 1010101, 100000000, 100000001, 100000100, 100000101, 100010000, 100010001, 100010100, 100010101, 101000000, 101000001
Offset: 0

Views

Author

Henry Bottomley, Jul 03 2001

Keywords

Comments

Numbers that are sums of distinct powers of 100. - David Wasserman, Feb 26 2008

Examples

			a(11)=1000101, since 11 in binary is 1011 and binary carryless sum of 1011000, 0, 10110 and 1011 is 1000101.
		

Crossrefs

Cf. Moser-de Bruijn sequence A000695, carryless decimal squares A059729, pre-carry binary squares A063009.

Programs

  • Mathematica
    With[{k = 100}, Map[FromDigits[#, k] &, Tuples[{0, 1}, 5]]] (* Michael De Vlieger, Oct 29 2022 *)
  • PARI
    a(n) = fromdigits(binary(n),100); \\ Ruud H.G. van Tol, Dec 05 2022
    
  • Python
    def A063010(n): return int(bin(int(bin(n)[2:],4))[2:]) # Chai Wah Wu, Apr 09 2025

Formula

a(n) = A062033(n)/10, i.e., with final zero removed.
a(n) = Sum_{k>=0} A030308(n,k)*A098608(k). - Philippe Deléham, Oct 15 2011
G.f.: (1/(1 - x))*Sum_{k>=0} 100^k*x^(2^k)/(1 + x^(2^k)). - Ilya Gutkovskiy, Jun 04 2017

Extensions

More terms from David Wasserman, Feb 26 2008

A168541 Numbers consisting of either 2's and 0's or 5's and 0's.

Original entry on oeis.org

2, 5, 20, 50, 200, 202, 220, 500, 505, 550, 2000, 2002, 2020, 2022, 2200, 2202, 2220, 5000, 5005, 5050, 5055, 5500, 5505, 5550, 20000, 20002, 20020, 20022, 20200, 20202, 20220, 20222, 22000, 22002, 22020, 22022, 22200, 22202, 22220, 50000, 50005
Offset: 1

Views

Author

Keywords

Comments

A subset of the divisors of zero in carryless arithmetic mod 10, e.g., 5 * 44 = 0.

Crossrefs

Programs

  • Mathematica
    lst = {2, 5}; k = 1; While[k < 10^5, id = Union@ IntegerDigits@k; len = Length@ id; If[ len == 2 && id == {0, 2} || id == {0, 5}, AppendTo[lst, k]]; k++ ]; lst (* Robert G. Wilson v, Jul 12 2010 *)
    Join[{2,5},Sort[Flatten[Table[Select[FromDigits/@Tuples[{k,0},6],DigitCount[ #,10,0]>0 && DigitCount[#,10,k]>0&],{k,{2,5}}]]]] (* Harvey P. Dale, Jul 03 2020 *)

Extensions

More terms from Robert G. Wilson v, Jul 12 2010

A169890 Carryless sum 1+2+3+...+n.

Original entry on oeis.org

0, 1, 3, 6, 0, 5, 1, 8, 6, 5, 15, 26, 38, 41, 55, 60, 76, 83, 91, 0, 20, 41, 63, 86, 0, 25, 41, 68, 86, 5, 35, 66, 98, 21, 55, 80, 16, 43, 71, 0, 40, 81, 23, 66, 0, 45, 81, 28, 66, 5, 55, 6, 58, 1, 55, 0, 56, 3, 51, 0, 60, 21, 83, 46, 0, 65, 21, 88, 46, 5, 75, 46, 18, 81, 55, 20, 96, 63, 31
Offset: 0

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Author

Keywords

Comments

Carryless analog of triangular numbers.

Crossrefs

A339023 Replace each digit d in the decimal representation of n with the digital root of n*d.

Original entry on oeis.org

0, 1, 4, 9, 7, 7, 9, 4, 1, 9, 10, 22, 36, 43, 52, 63, 76, 82, 99, 19, 40, 63, 88, 16, 36, 58, 73, 99, 28, 49, 90, 34, 61, 99, 31, 64, 99, 37, 67, 99, 70, 25, 63, 13, 55, 99, 46, 85, 36, 79, 70, 36, 85, 46, 99, 55, 13, 63, 25, 79, 90, 67, 37, 99, 64, 31, 99, 61
Offset: 0

Views

Author

Sebastian Karlsson, Jan 18 2021

Keywords

Examples

			a(23) = 16 because 2*23 = 46 and 3*23 = 69 and the digital roots of 46 and 69 are 1 and 6.
		

Crossrefs

Programs

  • PARI
    dr(n) = if(n, (n-1)%9+1); \\ A010888
    a(n) = if (n==0, return(0)); my(d=digits(n), s=""); for (k=1, #d, s=concat(s, dr(n*d[k]))); eval(s); \\ Michel Marcus, Jan 18 2021
  • Python
    def digitalroot(n):
        return 0 if n == 0 else (n-1)%9 + 1
    def a(n):
        return int(''.join([str(digitalroot(n*int(d))) for d in str(n)]))
    for n in range(0, 68):
        print(a(n), end=', ')
    

Formula

a(9*n + 1) = 9*n + 1.
a(10*n) = 10*a(n). - Sebastian Karlsson, Feb 14 2021

A169916 Squares in carryless arithmetic mod 10 with addition and multiplication of digits both defined to be addition mod 10.

Original entry on oeis.org

0, 2, 4, 6, 8, 0, 2, 4, 6, 8, 220, 242, 264, 286, 208, 220, 242, 264, 286, 208, 440, 462, 484, 406, 428, 440, 462, 484, 406, 428, 660, 682, 604, 626, 648, 660, 682, 604, 626, 648, 880, 802, 824, 846, 868, 880, 802, 824, 846, 868, 0, 22, 44, 66, 88, 0, 22, 44, 66, 88, 220, 242
Offset: 0

Views

Author

Keywords

Comments

The rules of arithmetic used in A169916, A169917, A169918 have very strange consequences. Many of the familiar laws fail. For instance, the arithmetic in A169916 is not associative: 10*(9*2) = 10*1 = 21 != (10*9)*2 = 9*2 = 1.

Examples

			a(16) = 16*16 = 242:
....16
....16
------
....72 (6*6 = 6+6 mod 10 = 2, 6*1 = 6+1 mod 10 = 7)
...27.
------
...242
------
		

Crossrefs

The four versions are A059729, A169916, A169917, A169918.

Programs

  • PARI
    A169916(n)={u=vector(#n=digits(n),i,1);n=apply(d->n+d*u,n)%10;sum(i=0,2*#n-2,sum(j=max(1,#n-i),min(2*#n-1-i,#n),n[2*#n-i-j][j])%10*10^i)} \\ M. F. Hasler, Mar 26 2015

Formula

a(n)=a(n') if respective digits of n and n' differ by 0 or 5. In particular, a(10k+m) = a(10k+m+5) if 0 <= m <= 4.

A169917 Squares in carryless arithmetic mod 10 with addition and multiplication of digits both defined to be multiplication mod 10.

Original entry on oeis.org

0, 1, 4, 9, 6, 5, 6, 9, 4, 1, 100, 111, 144, 199, 166, 155, 166, 199, 144, 111, 400, 441, 464, 469, 446, 405, 446, 469, 464, 441, 900, 991, 964, 919, 946, 955, 946, 919, 964, 991, 600, 661, 644, 649, 666, 605, 666, 649, 644, 661, 500, 551, 504, 559, 506, 555, 506, 559, 504
Offset: 0

Views

Author

Keywords

Comments

The rules of arithmetic used in A169916, A169917, A169918 have very strange consequences. Many of the familiar laws fail. For instance, the arithmetic in A169916 is not associative: 10*(9*2) = 10*1 = 21 != (10*9)*2 = 9*2 = 1.

Examples

			a(24) = 24*24 = 446:
...24
...24
-----
...86
..48.
-----
..446
(The rule for "adding" the columns is to multiply mod 10: 8+8 = 8 * 8 mod 10 = 4.)
		

Crossrefs

The four versions are A059729, A169916, A169917, A169918.

Programs

  • PARI
    A169917(n)={#n=digits(n);n=apply(d->n*d,n)%10;sum(i=0,2*#n-2,prod(j=max(1,#n-i),min(2*#n-1-i,#n),n[2*#n-i-j][j])%10*10^i)} \\ M. F. Hasler, Mar 26 2015

Formula

a(n) = a(n') if the i-th digit of n' either equals the i-th digit of n or (10 - the i-th digit of n): e.g., a(12345) = a(18365), because the 2nd and 4th digit of 12345 equal 10-(the 2nd resp. 4th digit of 18365), and the other digits are the same. In particular, a(10k+5+m) = a(10k+5-m), for m=0,...,4. - M. F. Hasler, Mar 26 2015

A169963 Number of (2n+1)-digit squares in carryless arithmetic mod 10.

Original entry on oeis.org

5, 46, 452, 4504, 45008, 450016, 4500032, 45000064, 450000128, 4500000256, 45000000512, 450000001024, 4500000002048, 45000000004096, 450000000008192, 4500000000016384, 45000000000032768, 450000000000065536, 4500000000000131072, 45000000000000262144
Offset: 0

Views

Author

N. J. A. Sloane, Aug 07 2010

Keywords

Crossrefs

See A059729 for the actual squares.

Programs

  • Maple
    f :- n->2^((n-1)/2) + add( 5^d*2^((n+1)/2),d=0..(n-3)/2) + 2^((n+3)/2)*5^((n-1)/2);
  • Mathematica
    LinearRecurrence[{12, -20}, {5, 46}, 25] (* Paolo Xausa, Jun 26 2024 *)

Formula

For formula see Maple code.
a(n) = 12*a(n-1)-20*a(n-2). G.f.: -(14*x-5) / ((2*x-1)*(10*x-1)). - Colin Barker, May 11 2013

A361351 Carryless n-th powers of n base 10.

Original entry on oeis.org

1, 1, 4, 7, 6, 5, 6, 3, 6, 9, 10000000000, 115502205511, 1440046600466, 19225142754633, 166668888866666, 1555555555555555, 16000880008800066, 194006440028800877, 1422046880284402844, 11116222228888849999, 600000000000000000000, 2600042000840006800021
Offset: 0

Views

Author

Seiichi Manyama, Mar 09 2023

Keywords

Crossrefs

Programs

  • PARI
    a(n) = fromdigits(Vec(Pol(digits(n))^n)%10);

A169889 Numbers that are carryless squares in base 10.

Original entry on oeis.org

0, 1, 4, 5, 6, 9, 100, 105, 121, 126, 144, 149, 164, 169, 181, 186, 400, 405, 424, 429, 441, 446, 461, 466, 484, 489, 500, 501, 504, 505, 506, 509, 600, 605, 621, 626, 644, 649, 664, 669, 681, 686, 900, 905, 924, 929, 941, 946, 961, 966, 984, 989, 10000, 10005, 10104
Offset: 1

Views

Author

Keywords

Comments

A059729 sorted and duplicates removed.

Crossrefs

See A087019 (lunar squares) for another version.

A169903 Primitive primes in carryless arithmetic mod 10.

Original entry on oeis.org

21, 23, 25, 27, 29, 51, 56, 201, 209, 227, 229, 241, 243, 261, 263, 287, 289, 551, 2023, 2027, 2043, 2047, 2061, 2069, 2081, 2089, 2207, 2209, 2221, 2223, 2263, 2267, 2281, 2287, 2401, 2407, 2421, 2423, 2441, 2449, 2483, 2489, 2603, 2609
Offset: 1

Views

Author

Keywords

Comments

Define the units in carryless arithmetic mod 10 to be the numbers 1, 3, 7 and 9 (these divide any number). A prime is a number N, not a unit, whose only factorizations are of the form N = u * M, where u is a unit.
A prime is primitive if it is not the carryless product of a smaller prime and a unit.
A subsequence of A169887.

Crossrefs

Previous Showing 11-20 of 26 results. Next