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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A289618 a(n) = A289617(n) - A046645(n) = A005187(A001222(n)) - A046645(n).

Original entry on oeis.org

0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 1, 1, 0, 2, 0, 1, 0, 0, 0, 1, 0, 0, 1, 1, 1, 1, 0, 1, 1, 2, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 2, 1, 2, 1, 1, 0, 2, 0, 1, 0, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 1, 0, 0, 1, 1, 0, 0, 0, 1, 0, 2, 1, 1, 1, 2, 0, 2, 1, 0, 1, 1, 1, 1, 0, 0, 0, 1, 0, 1, 0, 2, 1, 1, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 0, 1, 1, 2
Offset: 1

Views

Author

Antti Karttunen, Jul 08 2017

Keywords

Crossrefs

Cf. A268375 (positions of zeros), A289619 (of ones).

Programs

Formula

a(n) = A289617(n) - A046645(n) = A005187(A001222(n)) - A046645(n).

A091862 a(n) = 1 if the sum of all exponents of the prime-factorization of n has no carries when summed in base 2, or a(n) = 0 if there are any carries.

Original entry on oeis.org

1, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 0, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 1, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 0, 1, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 0, 1, 1, 0, 0, 1, 1, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 1, 1, 1, 0, 1, 0, 1, 0, 0
Offset: 1

Views

Author

Leroy Quet, Mar 13 2004

Keywords

Comments

Characteristic function for A268375. - Antti Karttunen, Nov 23 2017

Examples

			a(12) = 1 because 12 = 2^2 *3^1 and, in base 2, 2 = '10', 1 = '1' and '10' and '1' have their ones in different positions. But a(24) = 0 because 24 = 2^3 *3^1 and in base 2 3 = '11', 1 = '1', which both share a rightmost one.
		

Crossrefs

Cf. A268375 (positions of ones), A268376 (of zeros).

Programs

  • Mathematica
    f[e_] := Position[Reverse[IntegerDigits[e, 2]], 1] // Flatten; a[n_] := Boole[UnsameQ @@ Flatten[f /@ FactorInteger[n][[;; , 2]]]]; Array[a, 100] (* Amiram Eldar, Dec 23 2023 *)
  • PARI
    a(n) = {my(e = factor(n)[,2], b = 0); for(i=1, #e, b = bitor(b, e[i])); n == 1 || b == vecsum(e);} \\ Amiram Eldar, Dec 23 2023

Formula

If A268374(n) = 0, then a(n) = 1, 0 otherwise. - Antti Karttunen, Nov 23 2017

Extensions

More terms from Pab Ter (pabrlos(AT)yahoo.com), May 25 2004

A268374 a(n) = A001222(n) - A267116(n).

Original entry on oeis.org

0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 1, 1, 0, 1, 0, 1, 0, 0, 0, 2, 0, 0, 1, 1, 1, 2, 0, 1, 1, 1, 0, 2, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 1, 1, 1, 1, 1, 0, 1, 0, 1, 0, 0, 1, 2, 0, 0, 1, 2, 0, 2, 0, 1, 0, 0, 1, 2, 0, 0, 0, 1, 0, 1, 1, 1, 1, 1, 0, 1, 1, 0, 1, 1, 1, 1, 0, 0, 0, 2, 0, 2, 0, 1, 2, 1, 0, 2, 0, 2, 1, 0, 0, 2, 1, 0, 0, 1, 1, 2
Offset: 1

Views

Author

Antti Karttunen, Feb 03 2016

Keywords

Crossrefs

Cf. A268375 (indices of zeros), A268376 (of nonzeros).

Programs

Formula

a(n) = A001222(n) - A267116(n).

A318363 Multiplicative with a(prime(i)^k) = prime(k)^2^(i-1).

Original entry on oeis.org

1, 2, 4, 3, 16, 8, 256, 5, 9, 32, 65536, 12, 4294967296, 512, 64, 7, 18446744073709551616, 18, 340282366920938463463374607431768211456, 48, 1024, 131072, 115792089237316195423570985008687907853269984665640564039457584007913129639936, 20, 81, 8589934592, 25
Offset: 1

Views

Author

Rémy Sigrist, Aug 24 2018

Keywords

Comments

This sequence has similarities with A048767.
This sequence is injective (all terms are distinct).
This sequence is a permutation of A268375.

Crossrefs

Programs

  • Mathematica
    Array[Apply[Times, FactorInteger[#] /. {p_, k_} /; p > 1 :> Prime[k]^2^(PrimePi[p] - 1)] &, 27] /. {1, 1} -> 1 (* Michael De Vlieger, Aug 25 2018 *)
  • PARI
    a(n) = my (f=factor(n)); prod(i=1, #f~, prime(f[i,2])^2^(primepi(f[i,1])-1))

Formula

A007947(a(n)) = A007947(A048767(n)) for any n > 0.
a(A005117(n)) = 2^A048672(n) for any n > 0.

A355935 Dirichlet inverse of A091862, characteristic function of numbers for which A267116(n) = bigomega(n), where A267116 is the bitwise-OR of the exponents of primes in the prime factorization of n.

Original entry on oeis.org

1, -1, -1, 0, -1, 2, -1, 0, 0, 2, -1, -2, -1, 2, 2, 0, -1, -2, -1, -2, 2, 2, -1, 2, 0, 2, 0, -2, -1, -6, -1, 0, 2, 2, 2, 6, -1, 2, 2, 2, -1, -6, -1, -2, -2, 2, -1, -2, 0, -2, 2, -2, -1, 2, 2, 2, 2, 2, -1, 10, -1, 2, -2, 0, 2, -6, -1, -2, 2, -6, -1, -8, -1, 2, -2, -2, 2, -6, -1, -2, 0, 2, -1, 10, 2, 2, 2, 2, -1, 10, 2, -2, 2, 2, 2, 2, -1, -2, -2, 6, -1, -6, -1, 2, -6
Offset: 1

Views

Author

Antti Karttunen, Jul 21 2022

Keywords

Crossrefs

Programs

  • Mathematica
    s[n_] := If[n == 1 || PrimeOmega[n] == BitOr @@ FactorInteger[n][[;; , 2]], 1, 0]; a[1] = 1; a[n_] := a[n] = -DivisorSum[n, s[n/#]*a[#] &, # < n &]; Array[a, 100] (* Amiram Eldar, Jul 21 2022 *)
  • PARI
    A267116(n) = if(1==n, 0, fold(bitor, factor(n)[, 2]));
    A091862(n) = (bigomega(n)==A267116(n));
    memoA355935 = Map();
    A355935(n) = if(1==n,1,my(v); if(mapisdefined(memoA355935,n,&v), v, v = -sumdiv(n,d,if(dA091862(n/d)*A355935(d),0)); mapput(memoA355935,n,v); (v)));

Formula

a(1) = 1, and for n > 1, a(n) = -Sum_{d|n, dA091862(n/d) * a(d).
Previous Showing 11-15 of 15 results.