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 1-8 of 8 results.

A183534 Square array of generalized Ulam numbers U(n,k), n>=1, k>=2, read by antidiagonals: U(n,k) = n if n<=k; for n>k, U(n,k) = least number > U(n-1,k) which is a unique sum of k distinct terms U(i,k) with i

Original entry on oeis.org

1, 1, 2, 1, 2, 3, 1, 2, 3, 4, 1, 2, 3, 6, 6, 1, 2, 3, 4, 9, 8, 1, 2, 3, 4, 10, 10, 11, 1, 2, 3, 4, 5, 16, 11, 13, 1, 2, 3, 4, 5, 15, 17, 12, 16, 1, 2, 3, 4, 5, 6, 25, 18, 28, 18, 1, 2, 3, 4, 5, 6, 21, 26, 19, 29, 26, 1, 2, 3, 4, 5, 6, 7, 36, 27, 22, 30, 28, 1, 2, 3, 4, 5, 6, 7, 28, 37, 28, 64, 53, 36
Offset: 1

Views

Author

Keywords

Comments

The columns are Ulam-type sequences - see A002858 for further information. Some of these sequences - but not all - seem to have quite simple generating functions.
U(k+1,k) = k*(k+1)/2.
U(k+2+j,k) = k^2+j for k>=3 and 0<=j
U(2*k+2,k) = k*(3*k-1)/2 for k>=3.

Examples

			Square array U(n,k) begins:
  1,  1,  1,  1,  1,  1,  ...
  2,  2,  2,  2,  2,  2,  ...
  3,  3,  3,  3,  3,  3,  ...
  4,  6,  4,  4,  4,  4,  ...
  6,  9, 10,  5,  5,  5,  ...
  8, 10, 16, 15,  6,  6,  ...
		

Crossrefs

Programs

  • Maple
    b:= proc(n,i,k,h) option remember;
          local t;
          if n<0 or h<0 then 0
        elif n=0 then `if`(h=0, 1, 0)
        elif i=0 or h=0 then 0
        elif h=1 then t:= v(n, k);
                      `if`(t>0 and t<=i, 1, 0)
                 else t:= b(n -U(i, k), i-1, k, h-1);
                      t+ `if`(t>1, 0, b(n, i-1, k, h))
          fi
        end:
    v:= proc() 0 end:
    U:= proc(n,k) option remember;
          local m;
          if n<=k then v(n,k):= n
                  else for m from U(n-1, k)+1
                         while b(m, n-1, k, k)<>1 do od;
                       v(m,k):= n; m
          fi
        end:
    seq(seq(U(n, 2+d-n), n=1..d), d=1..12);
  • Mathematica
    b[n_, i_, k_, h_] := b[n, i, k, h] = Module[{t}, Which[n < 0 || h < 0, 0, n == 0, If[h == 0, 1, 0], i == 0 || h == 0, 0, h == 1, t = v[n, k]; If[t > 0 && t <= i, 1, 0], True, t = b[n-U[i, k], i-1, k, h-1]; t+If[t > 1, 0, b[n, i-1, k, h]] ] ]; v[, ] = 0; U[n_, k_] := U[n, k] = Module[{m}, If[n <= k, v[n, k] = n, For[m = U[n-1, k]+1, b[m, n-1, k, k] != 1, m++]; v[m, k] = n; m] ]; Table[Table[U[n, 2+d-n], {n, 1, d}], {d, 1, 12}] // Flatten (* Jean-François Alcover, Dec 23 2013, translated from Maple *)
  • PARI
    Ulam(N,k=2,v=0)={ my( a=vector(k,i,i), c );
    for( n=k,N-1, for( t=1+a[n],9e9, c=0;
      forvec(v=vector(k,i,[i,n]),sum(j=1,k,a[v[j]])==t & c++>1 & next(2),2);
      c||next; v&print1(t","); a=concat(a,t); break;
    )); a}
    /* M. F. Hasler */

A183527 An Ulam-type sequence: a(n) = n if n<=4; for n>4, a(n) = least number > a(n-1) which is a unique sum of 4 distinct earlier terms.

Original entry on oeis.org

1, 2, 3, 4, 10, 16, 17, 18, 19, 22, 64, 65, 66, 68, 69, 128, 132, 188, 190, 191, 194, 252, 253, 255, 313, 314, 318, 374, 376, 377, 436, 441, 496, 497, 499, 500, 502, 560, 561, 563, 621, 622, 626, 682, 684, 685, 687, 745, 746, 805, 811
Offset: 1

Author

Keywords

Comments

An Ulam-type sequence - see A002858 for further information.

Examples

			a(5) = 10 = 1 + 2 + 3 + 4 = 4*5/2, because it is the least number >4 with a unique sum of 4 distinct earlier terms.
a(6) = 16 = 1 + 2 + 3 + 10 = 4^2, because it is the least number >10 with a unique sum of 4 distinct earlier terms.
		

Crossrefs

Programs

  • Maple
    # see A183534 for programs.

Formula

Conjectured G.f.: (-61*x^124-56*x^118+53*x^117+3*x^116 -x^115+2*x^114-65*x^113-58*x^112+57*x^111 -56*x^110-x^109-57*x^108+54*x^106 +3*x^105+58*x^104-52*x^102+50*x^101-55*x^100 +56*x^95-53*x^94-3*x^93+x^92-2*x^91 +2*x^90+x^87-x^86 +41*x^84-51*x^83-66*x^82-58*x^81 -52*x^79+4*x^78-58*x^77 -x^74-x^73-x^72-54*x^71 -6*x^70-59*x^69-x^68-58*x^67-2*x^66 -x^65-2*x^64-56*x^63-4*x^62-x^61 -58*x^60-2*x^59-59*x^58-x^57-x^56 -2*x^55-x^54-x^53-54*x^52-6*x^51 -59*x^50-x^49-58*x^48-2*x^47-x^46 -2*x^45-56*x^44-4*x^43-x^42-58*x^41 -2*x^40-x^39-58*x^38-2*x^37-x^36 -2*x^35-x^34-55*x^33-5*x^32-59*x^31 -x^30-2*x^29-56*x^28-4*x^27-x^26 -58*x^25-2*x^24-x^23-58*x^22-3*x^21 -x^20-2*x^19-56*x^18-4*x^17-59*x^16 -x^15-2*x^14-x^13-x^12-42*x^11 -3*x^10-x^9-x^8-x^7-6*x^6 -6*x^5-x^4-x^3-x^2-x) / (-x^74+x^73+x-1). (This has been verified for n up to 1000.)

A183533 An Ulam-type sequence: a(n) = n if n<=10; for n>10, a(n) = least number > a(n-1) which is a unique sum of 10 distinct earlier terms.

Original entry on oeis.org

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 55, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 145, 163, 190, 217, 235, 271, 280, 1740, 1741, 1744, 1745, 1799, 1804, 1805, 1824, 1825, 1831, 1859, 1869, 1913, 1914, 3554, 10521, 10522, 10526, 10527, 10537, 10563, 10564
Offset: 1

Author

Keywords

Comments

An Ulam-type sequence - see A002858 for further information.

Examples

			a(11) = 55 = 1 + ... + 10 = 10*11/2, because it is the least number >10 with a unique sum of 10 distinct earlier terms.
a(12) = 100 = 1 + ... + 9 + 55 = 10^2, because it is the least number >55 with a unique sum of 10 distinct earlier terms.
		

Crossrefs

Column k=10 of A183534.

Programs

  • Maple
    # see A183534 for programs.

A183532 An Ulam-type sequence: a(n) = n if n<=9; for n>9, a(n) = least number > a(n-1) which is a unique sum of 9 distinct earlier terms.

Original entry on oeis.org

1, 2, 3, 4, 5, 6, 7, 8, 9, 45, 81, 82, 83, 84, 85, 86, 87, 88, 89, 117, 133, 153, 177, 189, 221, 225, 1325, 1326, 1328, 1329, 1373, 1378, 1379, 1391, 1392, 1398, 1423, 1427, 2717, 2718, 4031, 4032, 4035, 4037, 4039, 5316, 5319, 5346, 5352, 5353, 5354, 5361
Offset: 1

Author

Keywords

Comments

An Ulam-type sequence - see A002858 for further information.

Examples

			a(10) = 45 = 1 + ... + 9 = 9*10/2, because it is the least number >9 with a unique sum of 9 distinct earlier terms.
a(11) = 81 = 1 + ... + 8 + 45 = 9^2, because it is the least number >45 with a unique sum of 9 distinct earlier terms.
		

Crossrefs

Column k=9 of A183534.

Programs

  • Maple
    # see A183534 for programs.

A183528 An Ulam-type sequence: a(n) = n if n<=5; for n>5, a(n) = least number > a(n-1) which is a unique sum of 5 distinct earlier terms.

Original entry on oeis.org

1, 2, 3, 4, 5, 15, 25, 26, 27, 28, 29, 35, 43, 45, 165, 171, 172, 174, 180, 181, 328, 333, 338, 339, 340, 341, 493, 499, 500, 647, 652, 657, 658, 659, 660, 661, 662, 663, 815, 818, 819, 971, 1127, 1137, 1138, 1139, 1140, 1141, 1142
Offset: 1

Author

Keywords

Comments

An Ulam-type sequence - see A002858 for further information.

Examples

			a(6) = 15 = 1 + 2 + 3 + 4 + 5 = 5*6/2, because it is the least number >5 with a unique sum of 5 distinct earlier terms.
a(7) = 25 = 1 + 2 + 3 + 4 + 15 = 5^2, because it is the least number >15 with a unique sum of 5 distinct earlier terms.
		

Crossrefs

Column k=5 of A183534.

Programs

  • Maple
    # see A183534 for programs.

A183529 An Ulam-type sequence: a(n) = n if n<=6; for n>6, a(n) = least number > a(n-1) which is a unique sum of 6 distinct earlier terms.

Original entry on oeis.org

1, 2, 3, 4, 5, 6, 21, 36, 37, 38, 39, 40, 41, 51, 61, 66, 284, 285, 289, 290, 297, 298, 299, 310, 312, 559, 561, 562, 570, 571, 574, 575, 834, 836, 837, 838, 839, 840, 841, 849, 850, 1109, 1124, 1125, 1126, 1127, 1386, 1401, 1402, 1661, 1676, 1677, 1936, 1951
Offset: 1

Author

Keywords

Comments

An Ulam-type sequence - see A002858 for further information.

Examples

			a(7) = 21 = 1 + ... + 6 = 6*7/2, because it is the least number >6 with a unique sum of 6 distinct earlier terms.
a(8) = 36 = 1 + ... + 5 + 21 = 6^2, because it is the least number >21 with a unique sum of 6 distinct earlier terms.
		

Crossrefs

Column k=6 of A183534.

Programs

  • Maple
    # see A183534 for programs.

A183530 An Ulam-type sequence: a(n) = n if n<=7; for n>7, a(n) = least number > a(n-1) which is a unique sum of 7 distinct earlier terms.

Original entry on oeis.org

1, 2, 3, 4, 5, 6, 7, 28, 49, 50, 51, 52, 53, 54, 55, 70, 82, 91, 109, 112, 555, 556, 563, 564, 572, 573, 576, 583, 584, 591, 593, 1103, 1104, 1105, 1111, 1112, 1124, 1632, 1637, 1642, 1643, 1648, 1653, 1654, 1655, 1656, 1657, 1660, 1661, 1662, 1671, 1672, 2184
Offset: 1

Author

Keywords

Comments

An Ulam-type sequence - see A002858 for further information.

Examples

			a(8) = 28 = 1 + ... + 7 = 7*8/2, because it is the least number >7 with a unique sum of 7 distinct earlier terms.
a(9) = 49 = 1 + ... + 6 + 28 = 7^2, because it is the least number >28 with a unique sum of 7 distinct earlier terms.
		

Crossrefs

Column k=7 of A183534.

Programs

  • Maple
    # see A183534 for programs.

A183531 An Ulam-type sequence: a(n) = n if n<=8; for n>8, a(n) = least number > a(n-1) which is a unique sum of 8 distinct earlier terms.

Original entry on oeis.org

1, 2, 3, 4, 5, 6, 7, 8, 36, 64, 65, 66, 67, 68, 69, 70, 71, 92, 106, 120, 141, 148, 792, 793, 802, 803, 816, 817, 820, 828, 830, 838, 844, 1591, 1592, 1606, 1607, 2356, 2357, 2358, 2359, 2360, 2384, 2395, 2402, 3149, 3150, 3169, 3919, 3920, 3921, 3922, 3923
Offset: 1

Author

Keywords

Comments

An Ulam-type sequence - see A002858 for further information.

Examples

			a(9) = 36 = 1 + ... + 8 = 8*9/2, because it is the least number >8 with a unique sum of 8 distinct earlier terms.
a(10) = 64 = 1 + ... + 7 + 36 = 8^2, because it is the least number >36 with a unique sum of 8 distinct earlier terms.
		

Crossrefs

Column k=8 of A183534.

Programs

  • Maple
    # see A183534 for programs.
Showing 1-8 of 8 results.