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 1-4 of 4 results.

A262504 First differences of A262502.

Original entry on oeis.org

1, 2, 4, 4, 6, 6, 8, 9, 10, 12, 12, 12, 12, 12, 16, 16, 16, 16, 18, 18, 18, 20, 20, 20, 20, 20, 20, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 30, 30, 30, 30, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 48
Offset: 0

Views

Author

Antti Karttunen, Sep 24 2015

Keywords

Comments

Which of the terms of A002183 occur here, and for how many times each?

Links

Crossrefs

Cf. A262502, A002183.

Programs

Formula

a(n) = A262502(n+1) - A262502(n).

A262503 a(n) = largest k such that A155043(k) = n.

Original entry on oeis.org

0, 2, 6, 12, 18, 22, 30, 34, 42, 48, 60, 72, 84, 96, 108, 120, 132, 140, 112, 116, 126, 124, 130, 138, 150, 156, 168, 180, 176, 184, 192, 204, 216, 228, 240, 248, 264, 280, 250, 258, 270, 288, 296, 312, 306, 320, 328, 340, 352, 364, 372, 354, 358, 368, 384, 396, 420, 402, 414, 418, 432, 450, 468, 480, 504, 520, 540, 560, 572, 580, 594, 612, 610, 618, 622, 628, 648, 672, 592
Offset: 0

Views

Author

Antti Karttunen, Sep 24 2015

Keywords

Comments

The first odd terms occur as a(121) = 1089, a(123) = 1093, a(349) = 3253, a(717) = 7581, a(807) = 8685, a(1225) = 13689, etc.

Links

Crossrefs

Cf. A261089 (gives the first occurrence of n in A155043).
Cf. A262507 (gives the number of times n occurs in A155043).
Cf. A259934, A262502.

Programs

  • Mathematica
    lim = 80; a[0] = 0; a[n_] := a[n] = 1 + a[n - DivisorSigma[0, n]]; t = Table[a@ n, {n, 0, 12 lim}]; Last@ Flatten@ Position[t, #] - 1 & /@ Range[0, lim] (* Uses the product of a limit and an arbitrary coefficient (12) based on observation of output for low values (n < 500). This might need to be adjusted for large n to give correct values of a(n). - Michael De Vlieger, Sep 29 2015 *) (* Note: one really should use a general safe limit, like A262502(n+2) I use in my Scheme-program. - Antti Karttunen, Sep 29 2015 *)
  • PARI
    allocatemem(123456789);
uplim = 2162160; \\ = A002182(41).
v155043 = vector(uplim);
v155043[1] = 1; v155043[2] = 1;
for(i=3, uplim, v155043[i] = 1 + v155043[i-numdiv(i)]);
A155043 = n -> if(!n,n,v155043[n]);
uplim2 = 110880; \\ = A002182(30).
v262503 = vector(uplim2);
for(i=1, uplim, if(v155043[i] <= uplim2, v262503[v155043[i]] = i));
A262503 = n -> if(!n,n,v262503[n]);
for(n=0, uplim2, write("b262503.txt", n, " ", A262503(n)));
  • Scheme
    (define (A262503 n) (let loop ((k (A262502 (+ 2 n)))) (if (= (A155043 k) n) k (loop (- k 1)))))

Formula

Other identities and observations. For all n >= 0:
A262502(n+2) > a(n). [Not rigorously proved, but empirical evidence and common sense agrees.]

A262507 a(n) = number of times n occurs in A155043.

Original entry on oeis.org

1, 2, 3, 5, 4, 5, 6, 4, 4, 4, 8, 4, 4, 5, 8, 7, 7, 7, 7, 8, 5, 6, 6, 8, 10, 7, 8, 7, 7, 5, 5, 6, 6, 8, 6, 7, 7, 7, 4, 5, 5, 6, 6, 8, 7, 5, 5, 6, 7, 11, 5, 4, 5, 8, 12, 7, 9, 5, 8, 8, 9, 10, 14, 11, 12, 11, 9, 11, 13, 12, 12, 11, 11, 11, 12, 12, 10, 9, 9, 9, 8, 6, 10, 9, 10, 8, 7, 7, 8, 11, 10, 10, 12, 9, 7, 6, 5, 5, 5, 5, 4, 7, 8, 6, 7, 9, 7, 5, 11, 13, 13, 8, 10, 12, 13, 10, 12, 16, 9, 8, 12
Offset: 0

Views

Author

Antti Karttunen, Sep 25 2015

Keywords

Comments

Records are: 1, 2, 3, 5, 6, 8, 10, 11, 12, 14, 16, 17, 19, 21, 22, 24, 25, 26, 27, 31, 35, 39, 44, ... and they occur at positions: 0, 1, 2, 3, 6, 10, 24, 49, 54, 62, 117, 236, 445, 484, 892, 893, 1022, 1784, 1911, 1912, 1913, 20600, 50822, ...
a(n) gives the length of each row of irregular table A263265.

Links

Crossrefs

Cf. A000005, A060990, A155043, A262502, A262505, A263265, A263270, A263279, A263280.
Cf. A261089, A262503.
Cf. A262508 (positions of ones).
Cf. A263260 (partial sums).

Programs

  • PARI
    allocatemem(123456789);
uplim = 2162160; \\ = A002182(41).
v155043 = vector(uplim);
v155043[1] = 1; v155043[2] = 1;
for(i=3, uplim, v155043[i] = 1 + v155043[i-numdiv(i)]);
uplim2 = 110880; \\ = A002182(30).
v262507 = vector(uplim2);
for(i=1, uplim, if(v155043[i] <= uplim2, v262507[v155043[i]]++));
A262507 = n -> if(!n,1,v262507[n]);
for(n=0, uplim2, write("b262507.txt", n, " ", A262507(n)));
  • Scheme
    (define (A262507 n) (add (lambda (k) (if (= (A155043 k) n) 1 0)) n (A262502 (+ 2 n))))
;; Auxiliary function add implements sum_{i=lowlim..uplim} intfun(i)
(define (add intfun lowlim uplim) (let sumloop ((i lowlim) (res 0)) (cond ((> i uplim) res) (else (sumloop (1+ i) (+ res (intfun i)))))))

Formula

a(n) = Sum_{k=n..A262502(2+n)} [A155043(k) == n]. (Here [...] denotes the Iverson bracket, resulting 1 when A155043(k) is n and 0 otherwise.)
Other identities. For all n >= 0:
a(n) = A263279(n) + A263280(n).

A261104 a(0)=0; for n >= 1, a(n) = 1 + a(n-A070319(n)), where A070319(n) is the maximum value for A000005 (number of divisors) in range 1 .. n.

Original entry on oeis.org

0, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 4, 3, 4, 4, 4, 4, 5, 4, 5, 5, 5, 5, 6, 5, 6, 5, 6, 6, 6, 6, 7, 6, 7, 6, 7, 7, 7, 7, 7, 8, 7, 8, 7, 8, 8, 8, 8, 8, 8, 9, 8, 9, 8, 9, 9, 9, 9, 9, 9, 9, 9, 10, 9, 10, 9, 10, 10, 10, 10, 10, 10, 10, 10, 11, 10, 11, 10, 11, 11, 11, 11, 11, 11, 11, 11, 12, 11, 12, 11, 12, 12, 12, 12, 12, 12, 12, 12, 13, 12, 13, 12, 13, 13, 13, 13, 13, 13, 13, 13, 14, 13, 14, 13, 14, 14, 14, 14, 14, 14, 14, 14
Offset: 0

Views

Author

Antti Karttunen, Sep 24 2015

Keywords

Comments

Number of steps needed to reach zero when starting from k = n and repeatedly applying the map that replaces k by k - A070319(k), where A070319(k) is the maximum value for A000005 (number of divisors) in range 1 .. k.

Links

Crossrefs

Cf. A155043, A070319.
Cf. A262502 (positions of records).

Formula

a(0)=0; for n >= 1, a(n) = 1 + a(n-A070319(n)).
Other identities. For all n >= 0:
a(A262502(n)) = n.
Showing 1-4 of 4 results.

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