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.

A278505 Square array constructed from Flavius sieve: Each row n (n >= 1) starts with A000960(n), followed by all numbers removed at the stage n of the sieve.

Original entry on oeis.org

1, 2, 3, 4, 5, 7, 6, 11, 9, 13, 8, 17, 21, 15, 19, 10, 23, 33, 37, 25, 27, 12, 29, 45, 55, 51, 31, 39, 14, 35, 57, 75, 85, 73, 43, 49, 16, 41, 69, 97, 111, 121, 99, 61, 63, 18, 47, 81, 115, 145, 159, 151, 127, 67, 79, 20, 53, 93, 135, 171, 199, 211, 193, 163, 87, 91, 22, 59, 105, 157, 205, 243, 267, 271, 247, 187, 103, 109
Offset: 1

Views

Author

Antti Karttunen, Nov 23 2016

Keywords

Comments

The array A(row,col) is read by descending antidiagonals A(1,1), A(1,2), A(2,1), A(1,3), A(2,2), A(3,1), ...

Examples

			The top left corner of the array:
   1,  2,   4,   6,   8,  10,  12,  14,  16,  18
   3,  5,  11,  17,  23,  29,  35,  41,  47,  53
   7,  9,  21,  33,  45,  57,  69,  81,  93, 105
  13, 15,  37,  55,  75,  97, 115, 135, 157, 175
  19, 25,  51,  85, 111, 145, 171, 205, 231, 265
  27, 31,  73, 121, 159, 199, 243, 283, 327, 367
  39, 43,  99, 151, 211, 267, 319, 379, 433, 487
  49, 61, 127, 193, 271, 343, 421, 483, 559, 631
  63, 67, 163, 247, 339, 427, 519, 607, 691, 793
  79, 87, 187, 303, 403, 523, 639, 739, 853, 963
		

Crossrefs

Inverse: A278506.
Transpose: A278503.
Column 1: A000960, column 2: A100287 (apart from its initial 1), A099259 (differences).
Cf. A278538 (row index of n), A278539 (column index of n).
Cf. also arrays A278507 and A278511 (different variants).
Cf. also A255545 (an analogous array constructed for Lucky sieve).

Programs

Formula

A(row,1) = A000960(row); for col > 1, A(row,col) = A278507(row,col-1).
For all n >= 1, A(A278538(n), A278539(n)) = n.

A278507 Square array A(row,col) where row n lists the numbers removed in round n of Flavius sieve. Array is read by antidiagonals A(1,1), A(1,2), A(2,1), A(1,3), A(2,2), A(3,1), ...

Original entry on oeis.org

2, 4, 5, 6, 11, 9, 8, 17, 21, 15, 10, 23, 33, 37, 25, 12, 29, 45, 55, 51, 31, 14, 35, 57, 75, 85, 73, 43, 16, 41, 69, 97, 111, 121, 99, 61, 18, 47, 81, 115, 145, 159, 151, 127, 67, 20, 53, 93, 135, 171, 199, 211, 193, 163, 87, 22, 59, 105, 157, 205, 243, 267, 271, 247, 187, 103, 24, 65, 117, 175, 231, 283, 319, 343, 339, 303, 229, 123
Offset: 1

Views

Author

Antti Karttunen, Nov 23 2016

Keywords

Examples

			The top left corner of the array:
   2,   4,   6,   8,  10,  12,  14,  16,  18,   20
   5,  11,  17,  23,  29,  35,  41,  47,  53,   59
   9,  21,  33,  45,  57,  69,  81,  93, 105,  117
  15,  37,  55,  75,  97, 115, 135, 157, 175,  195
  25,  51,  85, 111, 145, 171, 205, 231, 265,  291
  31,  73, 121, 159, 199, 243, 283, 327, 367,  409
  43,  99, 151, 211, 267, 319, 379, 433, 487,  547
  61, 127, 193, 271, 343, 421, 483, 559, 631,  699
  67, 163, 247, 339, 427, 519, 607, 691, 793,  879
  87, 187, 303, 403, 523, 639, 739, 853, 963, 1081
		

Crossrefs

Transpose: A278508.
This is array A278505 without its leftmost column, A000960.
Column 1: A100287 (apart from its initial 1).
Cf. A278529 (column index of n), A278538 (row index of n).
Cf. A278492.
Cf. A255543 for analogous array for Lucky sieve.

Programs

Formula

A(1,col) = 2*col; for row > 1, A(row,col) = A278492(row-1,(col*(row+1))-1). [Note that unlike this array, A278492 uses zero-based indexing for its rows and columns.]

A278539 a(n) = index of the column where n is located in array A278505.

Original entry on oeis.org

1, 2, 1, 3, 2, 4, 1, 5, 2, 6, 3, 7, 1, 8, 2, 9, 4, 10, 1, 11, 3, 12, 5, 13, 2, 14, 1, 15, 6, 16, 2, 17, 4, 18, 7, 19, 3, 20, 1, 21, 8, 22, 2, 23, 5, 24, 9, 25, 1, 26, 3, 27, 10, 28, 4, 29, 6, 30, 11, 31, 2, 32, 1, 33, 12, 34, 2, 35, 7, 36, 13, 37, 3, 38, 5, 39, 14, 40, 1, 41, 8, 42, 15, 43, 4, 44, 2, 45, 16, 46, 1, 47, 9, 48, 17, 49, 6, 50, 3, 51, 18, 52, 2, 53
Offset: 1

Views

Author

Antti Karttunen, Nov 23 2016

Keywords

Comments

Ordinal transform of A278538 (as the rows of A278505 are strictly growing).

Crossrefs

One more than A278529.

Programs

Formula

a(n) = 1 + A278529(n).

A278504 Inverse permutation to A278503.

Original entry on oeis.org

1, 3, 2, 6, 5, 10, 4, 15, 8, 21, 9, 28, 7, 36, 12, 45, 14, 55, 11, 66, 13, 78, 20, 91, 17, 105, 16, 120, 27, 136, 23, 153, 19, 171, 35, 190, 18, 210, 22, 231, 44, 253, 30, 276, 26, 300, 54, 325, 29, 351, 24, 378, 65, 406, 25, 435, 34, 465, 77, 496, 38, 528, 37, 561, 90, 595, 47, 630, 43, 666, 104, 703, 31, 741, 33, 780, 119, 820, 46
Offset: 1

Views

Author

Antti Karttunen, Nov 23 2016

Keywords

Crossrefs

Inverse: A278503.
Cf. also A278506, A278512.

Programs

  • Scheme
    (define (A278504 n) (let ((row (A278539 n)) (col (A278538 n))) (* (/ 1 2) (- (expt (+ row col) 2) row col col col -2))))

Formula

a(n) = (1/2) * ((c+r)^2 - r - 3*c + 2), where c = A278538(n), and r = A278539(n).

A278506 Inverse permutation to A278505.

Original entry on oeis.org

1, 2, 3, 4, 5, 7, 6, 11, 9, 16, 8, 22, 10, 29, 14, 37, 12, 46, 15, 56, 13, 67, 17, 79, 20, 92, 21, 106, 23, 121, 27, 137, 18, 154, 30, 172, 19, 191, 28, 211, 38, 232, 35, 254, 24, 277, 47, 301, 36, 326, 26, 352, 57, 379, 25, 407, 31, 436, 68, 466, 44, 497, 45, 529, 80, 562, 54, 596, 39, 631, 93, 667, 34, 704, 32
Offset: 1

Views

Author

Antti Karttunen, Nov 23 2016

Keywords

Crossrefs

Inverse: A278505.
Cf. also A278504, A278512.

Programs

  • Scheme
    (define (A278506 n) (let ((row (A278538 n)) (col (A278539 n))) (* (/ 1 2) (- (expt (+ row col) 2) row col col col -2))))

Formula

a(n) = (1/2) * ((c+r)^2 - r - 3*c + 2), where c = A278539(n), and r = A278538(n).

A278511 Square array constructed from Flavius sieve, shifted version, read by descending antidiagonals.

Original entry on oeis.org

2, 4, 3, 6, 5, 7, 8, 11, 9, 13, 10, 17, 21, 15, 19, 12, 23, 33, 37, 25, 27, 14, 29, 45, 55, 51, 31, 39, 16, 35, 57, 75, 85, 73, 43, 49, 18, 41, 69, 97, 111, 121, 99, 61, 63, 20, 47, 81, 115, 145, 159, 151, 127, 67, 79, 22, 53, 93, 135, 171, 199, 211, 193, 163, 87, 91, 24, 59, 105, 157, 205, 243, 267, 271, 247, 187, 103, 109
Offset: 1

Views

Author

Antti Karttunen, Nov 23 2016

Keywords

Comments

Note how in comparison to A278505, the even numbers on the first row have been shifted one step left, "pushing" term 1 out of the array proper. This was done to obtain a better alignment with arrays like A083221 and A255127 associated with other sieves, from which one may then induce permutations by cross-referencing. (See also A255551.)

Examples

			The top left corner of the array:
   2,  4,   6,   8,  10,  12,  14,  16,  18,  20
   3,  5,  11,  17,  23,  29,  35,  41,  47,  53
   7,  9,  21,  33,  45,  57,  69,  81,  93, 105
  13, 15,  37,  55,  75,  97, 115, 135, 157, 175
  19, 25,  51,  85, 111, 145, 171, 205, 231, 265
  27, 31,  73, 121, 159, 199, 243, 283, 327, 367
  39, 43,  99, 151, 211, 267, 319, 379, 433, 487
  49, 61, 127, 193, 271, 343, 421, 483, 559, 631
  63, 67, 163, 247, 339, 427, 519, 607, 691, 793
  79, 87, 187, 303, 403, 523, 639, 739, 853, 963
		

Crossrefs

Inverse: A278512.
Cf. A000960 (column 1, but with its initial 1 replaced by 2), A278505, A278507.
Cf. A278538 (row index of n), A278537 (column index of n).
Cf. A083221, A255127, A255551 (analogous arrays constructed from other sieves).

Programs

Formula

A(1,col) = 2*col; For row > 1, A(row,1) = A000960(row) if col = 1, otherwise, A(row,col) = A278507(row,col-1).
For all n > 1, A(A278538(n), A278537(n)) = n.

A278512 Inverse permutation to A278511.

Original entry on oeis.org

1, 2, 4, 3, 6, 5, 7, 8, 10, 12, 9, 17, 11, 23, 15, 30, 13, 38, 16, 47, 14, 57, 18, 68, 21, 80, 22, 93, 24, 107, 28, 122, 19, 138, 31, 155, 20, 173, 29, 192, 39, 212, 36, 233, 25, 255, 48, 278, 37, 302, 27, 327, 58, 353, 26, 380, 32, 408, 69, 437, 45, 467, 46, 498, 81, 530, 55, 563, 40, 597, 94, 632, 35, 668, 33
Offset: 1

Views

Author

Antti Karttunen, Nov 23 2016

Keywords

Crossrefs

Inverse: A278511.
Cf. also A278504, A278506.

Formula

a(n) = (1/2) * ((c+r)^2 - r - 3*c + 2), where c = A278537(n) and r = A278538(n).

A278528 a(n) = number of the round in which n is removed in the Flavius sieve, 0 if it is never removed (when n is one of the terms of A000960).

Original entry on oeis.org

0, 1, 0, 1, 2, 1, 0, 1, 3, 1, 2, 1, 0, 1, 4, 1, 2, 1, 0, 1, 3, 1, 2, 1, 5, 1, 0, 1, 2, 1, 6, 1, 3, 1, 2, 1, 4, 1, 0, 1, 2, 1, 7, 1, 3, 1, 2, 1, 0, 1, 5, 1, 2, 1, 4, 1, 3, 1, 2, 1, 8, 1, 0, 1, 2, 1, 9, 1, 3, 1, 2, 1, 6, 1, 4, 1, 2, 1, 0, 1, 3, 1, 2, 1, 5, 1, 10, 1, 2, 1, 0, 1, 3, 1, 2, 1, 4, 1, 7, 1, 2, 1, 11, 1, 3, 1, 2, 1, 0, 1, 5, 1, 2, 1, 4, 1, 3, 1, 2, 1
Offset: 1

Views

Author

Antti Karttunen, Nov 23 2016

Keywords

Comments

a(n) = index of the row where n is located in array A278507, 0 if n does not occur there (when n is one of the terms of A000960).

Crossrefs

Cf. A278507, A278529 (the other index), A278538.
Cf. A000960 (positions of zeros).

Programs

  • Scheme
    ;; Very crude. Find it with two nested loops. (Maybe a closed form exists?)
    (define (A278528 n) (cond ((not (zero? (A278169 n))) 0) ((even? n) 1) (else (let searchrow ((row 2)) (let searchcol ((col 1)) (cond ((>= (A278507bi row col) n) (if (= (A278507bi row col) n) row (searchrow (+ 1 row)))) (else (searchcol (+ 1 col)))))))))
    ;; Code for A278507bi given in A278507.

Formula

Conjecture: a(n) = [C > 0] * C where we start with A := n, B := n - 1, C, m := 0 and until A = B consecutively apply m := m + 1, C := A - B, A := abs(A - m - (A mod m)), B := abs(B - m - (B mod m)). - Mikhail Kurkov, May 19 2025
Showing 1-8 of 8 results.