A246261 - OEIS

A246261

Numbers n such that A003961(n) is of the form 4k+1.

1, 3, 4, 9, 10, 11, 12, 13, 14, 16, 23, 25, 27, 30, 31, 33, 34, 35, 36, 37, 38, 39, 40, 42, 44, 47, 48, 49, 52, 56, 58, 59, 64, 69, 71, 75, 81, 82, 83, 85, 86, 89, 90, 92, 93, 95, 97, 99, 100, 102, 105, 106, 107, 108, 109, 110, 111, 114, 117, 119, 120, 121, 122, 124, 126, 130, 131, 132, 133, 134, 136, 139, 140, 141, 143, 144

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OFFSET

1,2

COMMENTS

Equally: numbers n for which A048673(n) is odd.

Also, after 1, numbers n for which A243062(n) is even.

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..10001

FORMULA

For all n >= 1, A246262(a(n)) = n.

MATHEMATICA

{1}~Join~Select[Range[144], Mod[Times @@ Map[NextPrime[#1]^#2 & @@ # &, FactorInteger[#]], 4] == 1 &] (* Michael De Vlieger, Mar 12 2021 *)

PROG

(Scheme, with Antti Karttunen's IntSeq-library)

(define A246261 (MATCHING-POS 1 1 (lambda (n) (= 1 (modulo (A003961 n) 4)))))

(Python)

from sympy import factorint, prime, primepi

from operator import mul

def a003961(n):

f=factorint(n)

return 1 if n==1 else reduce(mul, [prime(primepi(i) + 1)**f[i] for i in f])

print([n for n in range(1, 201) if a003961(n)%4==1]) # Indranil Ghosh, Jun 12 2017

CROSSREFS

Complement: A246263.

Positions of zeros in A246271.

Inverse function: A246262.

The first row of array A246259.

Cf. A003961, A048673, A243062, A246265.

Sequence in context: A307992 A323180 A095047 * A220695 A079258 A134025

Adjacent sequences: A246258 A246259 A246260 * A246262 A246263 A246264

KEYWORD

nonn

AUTHOR

Antti Karttunen, Aug 21 2014

STATUS

approved