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A286260 Compound filter: a(n) = P(A001511(n), A161942(n)), where P(n,k) is sequence A000027 used as a pairing function. 7
1, 8, 1, 39, 4, 8, 1, 157, 79, 47, 4, 39, 22, 8, 4, 600, 37, 782, 11, 256, 1, 47, 4, 157, 466, 233, 11, 39, 106, 47, 1, 2284, 4, 380, 4, 4281, 172, 122, 22, 1132, 211, 8, 56, 256, 742, 47, 4, 600, 1597, 4373, 37, 1278, 352, 122, 37, 157, 11, 1037, 106, 256, 466, 8, 79, 8785, 211, 47, 137, 2083, 4, 47, 37, 19507, 667, 1655, 466, 669, 4, 233, 11, 4661, 7261 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..16384

MathWorld, Pairing Function

FORMULA

a(n) = (1/2)*(2 + ((A001511(n)+A161942(n))^2) - A001511(n) - 3*A161942(n)).

PROG

(PARI)

A001511(n) = (1+valuation(n, 2));

A000265(n) = (n >> valuation(n, 2));

A161942(n) = A000265(sigma(n));

A286260(n) = (2 + ((A001511(n)+A161942(n))^2) - A001511(n) - 3*A161942(n))/2;

for(n=1, 16384, write("b286260.txt", n, " ", A286260(n)));

(Scheme) (define (A286260 n) (* (/ 1 2) (+ (expt (+ (A001511 n) (A161942 n)) 2) (- (A001511 n)) (- (* 3 (A161942 n))) 2)))

(Python)

from sympy import factorint, divisors, divisor_sigma

def T(n, m): return ((n + m)**2 - n - 3*m + 2)/2

def a000265(n): return max(list(filter(lambda i: i%2 == 1, divisors(n))))

def a161942(n): return a000265(divisor_sigma(n))

def a001511(n): return 2 + bin(n - 1)[2:].count("1") - bin(n)[2:].count("1")

def a(n): return T(a001511(n), a161942(n)) # Indranil Ghosh, May 07 2017

CROSSREFS

Cf. A000027, A001511, A161942, A286161, A286162, A286259, A286034.

Sequence in context: A050302 A341739 A286919 * A226374 A050401 A333403

Adjacent sequences:  A286257 A286258 A286259 * A286261 A286262 A286263

KEYWORD

nonn

AUTHOR

Antti Karttunen, May 07 2017

STATUS

approved

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Last modified April 11 21:52 EDT 2021. Contains 342888 sequences. (Running on oeis4.)