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A341609 Characteristic function of A337372: a(n) = 1 if A337345(n) = 1, otherwise 0. 3
0, 0, 0, 1, 0, 1, 0, 0, 1, 1, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET

1

COMMENTS

Characteristic function of the primitive terms of A246282.

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..65537

Index entries for characteristic functions

Index entries for sequences computed from indices in prime factorization

FORMULA

a(n) = [A337345(n) = 1], where [ ] is the Iverson bracket.

MATHEMATICA

f[1] = 1; f[n_] := Times @@ (NextPrime[#1]^#2 & @@@ FactorInteger[n]); a[n_] := Boole[DivisorSum[n, 1 &, f[#] > 2*# &] == 1]; Array[a, 100] (* Amiram Eldar, Feb 22 2021 *)

PROG

(PARI)

A003961(n) = { my(f = factor(n)); for (i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); factorback(f); };

A341609(n) = if(A003961(n) < 2*n, 0, fordiv(n, d, if((d<n)&&(A003961(d) > 2*d), return(0))); (1)); \\ After code in A341619

CROSSREFS

Cf. A003961, A246282, A337345, A337372.

Cf. also A341619.

Sequence in context: A038189 A072783 A288377 * A064911 A174898 A099618

Adjacent sequences:  A341606 A341607 A341608 * A341610 A341611 A341612

KEYWORD

nonn

AUTHOR

Antti Karttunen, Feb 22 2021

STATUS

approved

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Last modified January 24 13:48 EST 2022. Contains 350538 sequences. (Running on oeis4.)