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 1-6 of 6 results.

A020331 Numbers whose base-3 representation is the juxtaposition of two identical strings.

Original entry on oeis.org

4, 8, 30, 40, 50, 60, 70, 80, 252, 280, 308, 336, 364, 392, 420, 448, 476, 504, 532, 560, 588, 616, 644, 672, 700, 728, 2214, 2296, 2378, 2460, 2542, 2624, 2706, 2788, 2870, 2952, 3034, 3116, 3198, 3280, 3362, 3444, 3526, 3608, 3690, 3772, 3854, 3936, 4018
Offset: 1

Views

Author

David W. Wilson, Melia Aldridge (ma38(AT)spruce.evansville.edu)

Keywords

Examples

			50_10 = 1212_3. - _Jon E. Schoenfield_, Feb 11 2021

Links

Crossrefs

Cf. A020330, A020332, A020333, A020334, A020335, A020336, A020337, A020338.

Programs

  • Mathematica
    b3iQ[n_]:=Module[{idn3=IntegerDigits[n,3],len},len=Length[idn3];EvenQ[ len] && Take[idn3,len/2]==Take[idn3,-len/2 ]]; Select[Range[5000],b3iQ] (* Harvey P. Dale, Feb 08 2015 *)
a[n_] := n + n*3^Floor[Log[3, n] + 1]; Array[a, 50] (* Amiram Eldar, Apr 06 2021 *)

Formula

a(n) = n*3^floor(log_3(n)+1) + n. - Ilya Gutkovskiy, Jan 26 2018

A020333 Numbers whose base-5 representation is the juxtaposition of two identical strings.

Original entry on oeis.org

6, 12, 18, 24, 130, 156, 182, 208, 234, 260, 286, 312, 338, 364, 390, 416, 442, 468, 494, 520, 546, 572, 598, 624, 3150, 3276, 3402, 3528, 3654, 3780, 3906, 4032, 4158, 4284, 4410, 4536, 4662, 4788, 4914, 5040, 5166, 5292, 5418, 5544, 5670, 5796, 5922, 6048
Offset: 1

Views

Author

David W. Wilson, Melia Aldridge (ma38(AT)spruce.evansville.edu)

Keywords

Examples

			182_10 = 1212_5. - _Jon E. Schoenfield_, Feb 11 2021

Links

Crossrefs

Cf. A020330, A020331, A020332, A020334, A020335, A020336, A020337, A020338.

Programs

  • Mathematica
    tis5Q[n_]:=Module[{idn=IntegerDigits[n,5],len},len=Length[idn];EvenQ[len] && Take[idn,len/2]==Take[idn,-len/2]]; Select[Range[6500],tis5Q]  (* or *) Flatten[Table[FromDigits[#,5]&/@Select[(Flatten[{#,#}]&/@Tuples[ Range[ 0,4],n]),#[[1]]!=0&],{n,3}]] (* The second program is significantly faster than the first. *) (* Harvey P. Dale, Apr 08 2013 *)
a[n_] := n + n*5^Floor[Log[5, n] + 1]; Array[a, 50] (* Amiram Eldar, Apr 06 2021 *)
  • Python
    from itertools import count, product
def agen():
    for d in count(1):
        for first in "1234":
            for p in product("01234", repeat=d-1):
                yield int((first+"".join(p))*2, 5)
g = agen()
print([next(g) for n in range(1, 49)]) # Michael S. Branicky, Jun 12 2021

Formula

a(n) = n*5^floor(log_5(n)+1) + n. - Ilya Gutkovskiy, Jan 26 2018

A020334 Numbers whose base-6 representation is the juxtaposition of two identical strings.

Original entry on oeis.org

7, 14, 21, 28, 35, 222, 259, 296, 333, 370, 407, 444, 481, 518, 555, 592, 629, 666, 703, 740, 777, 814, 851, 888, 925, 962, 999, 1036, 1073, 1110, 1147, 1184, 1221, 1258, 1295, 7812, 8029, 8246, 8463, 8680, 8897, 9114, 9331, 9548, 9765, 9982, 10199, 10416
Offset: 1

Views

Author

David W. Wilson, Melia Aldridge (ma38(AT)spruce.evansville.edu)

Keywords

Examples

			296_10 = 1212_6. - _Jon E. Schoenfield_, Feb 11 2021

Links

Crossrefs

Cf. A020330, A020331, A020332, A020333, A020335, A020336, A020337, A020338.

Programs

  • Mathematica
    jtiQ[n_]:=Module[{idn6=IntegerDigits[n,6],len},len=Length[idn6];EvenQ[ len] && Take[idn6,len/2]==Take[idn6,(-len/2)]]; Select[ Range[ 11000], jtiQ] (* Harvey P. Dale, May 29 2016 *)
a[n_] := n + n*6^Floor[Log[6, n] + 1]; Array[a, 50] (* Amiram Eldar, Apr 06 2021 *)

Formula

a(n) = n*6^floor(log_6(n)+1) + n. - Ilya Gutkovskiy, Jan 26 2018

A020335 Numbers whose base-7 representation is the juxtaposition of two identical strings.

Original entry on oeis.org

8, 16, 24, 32, 40, 48, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000, 1050, 1100, 1150, 1200, 1250, 1300, 1350, 1400, 1450, 1500, 1550, 1600, 1650, 1700, 1750, 1800, 1850, 1900, 1950, 2000, 2050, 2100, 2150, 2200, 2250, 2300, 2350
Offset: 1

Views

Author

David W. Wilson, Melia Aldridge (ma38(AT)spruce.evansville.edu)

Keywords

Examples

			450_10 = 1212_7. - _Jon E. Schoenfield_, Feb 12 2021

Links

Crossrefs

Cf. A020330, A020331, A020332, A020333, A020334, A020336, A020337, A020338.

Programs

  • Mathematica
    a[n_] := n + n*7^Floor[Log[7, n] + 1]; Array[a, 50] (* Amiram Eldar, Apr 06 2021 *)

Formula

a(n) = n*7^floor(log_7(n)+1) + n. - Ilya Gutkovskiy, Jan 26 2018

A020336 Numbers whose base-8 representation is the juxtaposition of two identical strings.

Original entry on oeis.org

9, 18, 27, 36, 45, 54, 63, 520, 585, 650, 715, 780, 845, 910, 975, 1040, 1105, 1170, 1235, 1300, 1365, 1430, 1495, 1560, 1625, 1690, 1755, 1820, 1885, 1950, 2015, 2080, 2145, 2210, 2275, 2340, 2405, 2470, 2535, 2600, 2665, 2730, 2795, 2860, 2925, 2990, 3055
Offset: 1

Views

Author

David W. Wilson, Melia Aldridge (ma38(AT)spruce.evansville.edu)

Keywords

Examples

			650_10 = 1212_8. - _Jon E. Schoenfield_, Feb 12 2021

Links

Crossrefs

Cf. A020330, A020331, A020332, A020333, A020334, A020335, A020337, A020338.

Programs

  • Mathematica
    a[n_] := n + n*8^Floor[Log[8, n] + 1]; Array[a, 50] (* Amiram Eldar, Apr 06 2021 *)

Formula

a(n) = n*8^floor(log_8(n)+1) + n. - Ilya Gutkovskiy, Jan 26 2018

A020337 Numbers whose base-9 representation is the juxtaposition of two identical strings.

Original entry on oeis.org

10, 20, 30, 40, 50, 60, 70, 80, 738, 820, 902, 984, 1066, 1148, 1230, 1312, 1394, 1476, 1558, 1640, 1722, 1804, 1886, 1968, 2050, 2132, 2214, 2296, 2378, 2460, 2542, 2624, 2706, 2788, 2870, 2952, 3034, 3116, 3198, 3280, 3362, 3444, 3526, 3608, 3690, 3772
Offset: 1

Views

Author

David W. Wilson, Melia Aldridge (ma38(AT)spruce.evansville.edu)

Keywords

Examples

			902_10 = 1212_9. - _Jon E. Schoenfield_, Feb 12 2021

Links

Crossrefs

Cf. A020330, A020331, A020332, A020333, A020334, A020335, A020336, A020338.

Programs

  • Mathematica
    a[n_] := n + n*9^Floor[Log[9, n] + 1]; Array[a, 50] (* Amiram Eldar, Apr 06 2021 *)

Formula

a(n) = n*9^floor(log_9(n)+1) + n. - Ilya Gutkovskiy, Jan 26 2018
Showing 1-6 of 6 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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