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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A376401 a(n) = A276075(A376400(n)); Partial sums of A376400.

Original entry on oeis.org

0, 1, 3, 9, 39, 1089, 70814494839, 7568077812763134673885891483463343434987134201379042046671543939118568810481776089
Offset: 0

Views

Author

Antti Karttunen, Nov 02 2024

Keywords

Comments

a(8) has 2129 (decimal) digits.
From the second term onward also the partial sums of A376400.
By induction, it is easy to see that formula a(n) = A276075(A376400(n)) implies that from the second term onward, this sequence gives the partial sums of A376400, as A276075 is fully additive.

Crossrefs

Cf. also A143293 (when prepended with 0, an analogous sequence for A276085).

Programs

Formula

a(0) = 0; and for n >= 1, a(n) = a(n-1) + A376400(n-1) = Sum_{i=0..n-1} A376400(i).

A290249 Numbers that are the sum of distinct primorial numbers (A002110) (not including 1).

Original entry on oeis.org

2, 6, 8, 30, 32, 36, 38, 210, 212, 216, 218, 240, 242, 246, 248, 2310, 2312, 2316, 2318, 2340, 2342, 2346, 2348, 2520, 2522, 2526, 2528, 2550, 2552, 2556, 2558, 30030, 30032, 30036, 30038, 30060, 30062, 30066, 30068, 30240, 30242, 30246, 30248, 30270, 30272, 30276, 30278, 32340, 32342, 32346, 32348, 32370
Offset: 1

Views

Author

Ilya Gutkovskiy, Jul 24 2017

Keywords

Examples

			38 is in the sequence because 38 = 2 + 6 + 30 = 2 + 2*3 + 2*3*5.
		

Crossrefs

Programs

  • Mathematica
    Rest[f[x_] := Product[1 + x^Product[Prime[m], {m, 1, k}], {k, 1, 6}]; Exponent[#, x] & /@ List @@ Normal[Series[f[x], {x, 0, 32370}]]]

Formula

Nonzero exponents in expansion of Product_{k>=1} (1 + x^A002110(k)).

A328399 Lexicographically earliest infinite sequence such that a(i) = a(j) => A328475(i) = A328475(j) for all i, j.

Original entry on oeis.org

1, 1, 2, 1, 3, 2, 4, 4, 5, 1, 6, 2, 7, 7, 8, 4, 9, 5, 10, 10, 11, 7, 12, 8, 13, 13, 14, 10, 15, 11, 16, 16, 17, 16, 18, 17, 19, 19, 20, 1, 21, 2, 22, 22, 23, 4, 24, 5, 25, 25, 26, 7, 27, 8, 28, 28, 29, 10, 30, 11, 31, 31, 32, 31, 33, 32, 34, 34, 35, 16, 36, 17, 37, 37, 38, 19, 39, 20, 40, 40, 41, 22, 42, 23, 43, 43, 44, 25, 45, 26, 46, 46, 47, 46, 48, 47
Offset: 0

Views

Author

Antti Karttunen, Oct 19 2019

Keywords

Comments

Restricted growth sequence transform of A328475, defined as A328475(n) = A111701(A276086(n)).

Crossrefs

Cf. A002110, A053589, A111701, A276086, A143293 (indices of 1's after a(0)=1).
Cf. also A328477.

Programs

  • PARI
    up_to = 32768;
    rgs_transform(invec) = { my(om = Map(), outvec = vector(length(invec)), u=1); for(i=1, length(invec), if(mapisdefined(om,invec[i]), my(pp = mapget(om, invec[i])); outvec[i] = outvec[pp] , mapput(om,invec[i],i); outvec[i] = u; u++ )); outvec; };
    A111701(n) = forprime(p=2, , if(n%p, return(n), n /= p));
    A276086(n) = { my(m=1, p=2); while(n, m *= (p^(n%p)); n = n\p; p = nextprime(1+p)); (m); };
    A328475(n) = A111701(A276086(n));
    v328399 = rgs_transform(vector(up_to+1, n, A328475(n-1)));
    A328399(n) = v328399[1+n];

A343047 a(n) = A343046(n, n).

Original entry on oeis.org

0, 1, 6, 9, 12, 15, 210, 217, 246, 249, 252, 255, 420, 427, 456, 459, 492, 495, 630, 637, 666, 669, 702, 705, 840, 847, 876, 879, 912, 915, 30030, 30061, 30246, 30279, 30252, 30285, 32550, 32587, 32586, 32589, 32592, 32595, 32760, 32797, 32796, 32799, 32832
Offset: 0

Views

Author

Rémy Sigrist, Apr 05 2021

Keywords

Comments

This sequence has similarities with A087019 and A343043.

Examples

			For n = 2:
- the primorial base representation of 2 is "10", so:
         1 0
       x 1 0
       -----
         0 0
     + 1 0
     -------
       1 0 0
- hence a(2) = 2*3 = 6.
		

Crossrefs

Programs

  • PARI
    See Links section.

Formula

a(A002110(k)) = A002110(2*k) for any k >= 0.
a(A143293(k)) = A143293(2*k) for any k >= 0.

A343404 For any number n with representation (d_w, ..., d_1) in primorial base, a(n) is the least number m such that m mod prime(k) = d_k for k = 1..w (where prime(k) denotes the k-th prime number).

Original entry on oeis.org

0, 1, 4, 1, 2, 5, 6, 21, 16, 1, 26, 11, 12, 27, 22, 7, 2, 17, 18, 3, 28, 13, 8, 23, 24, 9, 4, 19, 14, 29, 120, 15, 190, 85, 50, 155, 36, 141, 106, 1, 176, 71, 162, 57, 22, 127, 92, 197, 78, 183, 148, 43, 8, 113, 204, 99, 64, 169, 134, 29, 30, 135, 100, 205
Offset: 0

Views

Author

Rémy Sigrist, Apr 14 2021

Keywords

Comments

Leading zeros in primorial base expansions are ignored.
The Chinese remainder theorem ensures that this sequence is well defined and provides a way to compute it.

Examples

			For n = 42 :
- the expansion of 42 in primary base is "1200",
- so a(42) mod 2 = 0 => a(42) = 2*t for some t >= 0,
     a(42) mod 3 = 0 => a(42) = 6*u for some u >= 0,
     a(42) mod 5 = 2 => a(42) = 12 + 30*v for some v >= 0,
     a(42) mod 7 = 1 => a(42) = 162 + 210*w for some w >= 0,
- we choose w=0 so as to minimize the value,
- hence a(42) = 162.
		

Crossrefs

Cf. A002110, A079276, A143293, A235168, A343405 (fixed points).

Programs

  • PARI
    a(n) = { my (v=Mod(0,1)); forprime (p=2, oo, if (n==0, return (lift(v)), v=chinese(v, Mod(n, p)); n\=p)) }

Formula

a(n) = 1 iff n belongs to A143293.
a(n) = n iff n belongs to A343405.
a(n) < A002110(k) for any n < A002110(k) and k >= 0.
a(A002110(k)) = A079276(k+1) * A002110(k) for any k >= 0.

A369243 a(n) is the least integer k whose arithmetic derivative is equal to the n-th partial sum of primorials, and 0 if no such k exists.

Original entry on oeis.org

2, 0, 14, 45, 198, 5114, 65174, 1086194, 20485574, 465779078, 0, 293420849770, 318745032938881
Offset: 0

Views

Author

Antti Karttunen, Jan 19 2024

Keywords

Comments

a(n) = the smallest integer k for which A003415(k) = A143293(n), and 0 if no such k exists.

Examples

			a(0) = 2 as the least number k such that A003415(k) = A143293(0) = 1 is 2.
a(1) = 0 as there is no number k such that A003415(k) = A143293(1) = 3.
		

Crossrefs

Cf also A368703.

Formula

a(n) <= A369244(n).

A369244 a(n) is the greatest integer k whose arithmetic derivative is equal to the n-th partial sum of primorials, and 0 if no such k exists.

Original entry on oeis.org

0, 14, 74, 198, 10295, 65174, 40354813, 20485574, 680909375411, 0, 17866904665985941, 318745032938881
Offset: 1

Views

Author

Antti Karttunen, Jan 19 2024

Keywords

Comments

a(n) = the largest integer k for which A003415(k) = A143293(n), and 0 if no such k exists.

Crossrefs

Cf. also A368704.

Formula

a(n) >= A369243(n).

A373603 The second smallest k such that A003415(k) == A276086(k) mod A002110(n), or -1 if no such k exists, where A003415 is the arithmetic derivative, A276086 is the primorial base exp-function, and A002110 gives the n-th primorial.

Original entry on oeis.org

2, 9, 26, 122, 1382, 21446, 204566, 9699686, 90387605
Offset: 1

Views

Author

Antti Karttunen, Jun 22 2024

Keywords

Comments

For n > 1, the index of the next term in A373849, after its sixth term 0, that is a multiple of A002110(n), as for n >= 1, the smallest k such that A003415(k) == A276086(k) mod A002110(n) gives the sequence 1, 6, 6, 6, 6, 6, 6, 6, ..., because A003415(6) = A276086(6).
Provided that such k exists for every n (and the escape clause is not needed), then the sequence is by necessity monotonic. If it is strictly monotonic, then it implies that k=6 is the only k such that A003415(k) = A276086(k). See also comments in A351228.
Note that if we instead search for the smallest k such that A276086(k) is a multiple of A002110(n) we obtain A143293, partial sums of the primorial numbers. See also A368703.

Crossrefs

Programs

  • PARI
    A002110(n) = prod(i=1,n,prime(i));
    A003415(n) = if(n<=1, 0, my(f=factor(n)); n*sum(i=1, #f~, f[i, 2]/f[i, 1]));
    A276086(n) = { my(m=1, p=2); while(n, m *= (p^(n%p)); n = n\p; p = nextprime(1+p)); (m); };
    A373603(n) = { my(m=A002110(n), c=2); for(i=1,oo,if(0==((A276086(i)-A003415(i))%m), c--; if(0==c, return(i)))); };

A376398 a(n) = A276085(n!), where A276085 is the primorial base log-function.

Original entry on oeis.org

0, 1, 3, 5, 11, 14, 44, 47, 51, 58, 268, 272, 2582, 2613, 2621, 2625, 32655, 32660, 543170, 543178, 543210, 543421, 10243111, 10243116, 10243128, 10245439, 10245445, 10245477, 233338347, 233338356, 6703031586, 6703031591, 6703031803, 6703061834, 6703061870, 6703061876, 207263552006, 207264062517, 207264064829, 207264064838
Offset: 1

Views

Author

Antti Karttunen, Oct 28 2024

Keywords

Crossrefs

Partial sums of A276085.
Cf. also A143293, A336415, A376397.

Programs

  • PARI
    A276085(n) = { my(f=factor(n)); sum(k=1, #f~, f[k, 2]*prod(i=1,primepi(f[k, 1]-1),prime(i))); };
    A376398(n) = A276085(n!);

Formula

a(n) = A276085(A000142(n)).
a(n) = Sum_{i=1..n} A276085(i).

A341433 Numbers that are divisible by the product of their digits in primorial base representation.

Original entry on oeis.org

1, 3, 9, 21, 39, 51, 99, 249, 261, 309, 669, 729, 2559, 2571, 2619, 2979, 3051, 4239, 7179, 7191, 32589, 32601, 32649, 32661, 33009, 33021, 37209, 37269, 37629, 51489, 92649, 92709, 93069, 97281, 272889, 274509, 543099, 543111, 543159, 543519, 543591, 544779
Offset: 1

Views

Author

Amiram Eldar, Feb 11 2021

Keywords

Comments

The primorial base repunits (A143293) are all terms since their product of digits in primorial base is 1.
All the terms are zeroless in primorial base, and therefore they are terms of A328574. In particular, since the last digit of even numbers in primorial base is 0, all the terms are odd numbers.

Examples

			9 is a term since 9 in primorial base is 111 (9 = 3! + 2! + 1!) and 9 is divisible by 1*1*1 = 1.
		

Crossrefs

A143293 is a subsequence.
Subsequence of A328574.

Programs

  • Mathematica
    max = 12; bases = Prime@Range[max, 1, -1]; nmax = Times @@ bases - 1; q[n_] := FreeQ[(d = IntegerDigits[n, MixedRadix[bases]]), 0] && Divisible[n, Times @@ d]; Select[Range[1, 10^5, 2], q]
Previous Showing 41-50 of 58 results. Next