A360506 - OEIS

A360506

Read A360505(n) as if it were a base-3 string and write it in base 10.

1, 7, 34, 358, 4003, 43369, 456712, 4708240, 47754961, 1339156591, 39693785002, 1169411930926, 34213667699203, 995038950807565, 28790341783585180, 829295063367580492, 23793774263808446005, 680307709052882601259, 19390954850541496025998

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OFFSET

1,2

COMMENTS

This has the same relationship to A360505 as A048435 does to A360502.

The primes in A048435 are in A360503. What are the primes in the present sequence?

Answer: The first primes are a(2) = 7, a(5) = 4003, a(13) = 34213667699203, a(57) and a(109). See A360507. - Rémy Sigrist, Feb 18 2023

LINKS

Winston de Greef, Table of n, a(n) for n = 1..407

Index entries for sequences related to Most Wanted Primes video

FORMULA

a(n) = A028898(A360505(n)). - Rémy Sigrist, Feb 18 2023

EXAMPLE

A360505(4) = 111021 and 111021_3 = 358_10 = a(4).

PROG

(PARI) a(n) = fromdigits(concat([digits(k, 3) | k <- Vecrev([1..n])]), 3) \\ Rémy Sigrist, Feb 18 2023

(Python)

from sympy.ntheory import digits

def a(n): return int("".join("".join(map(str, digits(k, 3)[1:])) for k in range(n, 0, -1)), 3)

print([a(n) for n in range(1, 21)]) # Michael S. Branicky, Feb 19 2023

(Python) # faster version for initial segment of sequence

from sympy.ntheory import digits

from itertools import count, islice

def agen(s=""): yield from (int(s:="".join(map(str, digits(n, 3)[1:]))+s, 3) for n in count(1))

print(list(islice(agen(), 20))) # Michael S. Branicky, Feb 19 2023

(Python)

from itertools import count, islice

def A360506_gen(): # generator of terms

a, b, c = 3, 1, 0

for i in count(1):

if i >= a:

a *= 3

c += i*b

yield c

b *= a

A360506_list = list(islice(A360506_gen(), 30)) # Chai Wah Wu, Nov 08 2023

CROSSREFS

Cf. A048435, A028898, A360502, A360503, A360505, A360507.

Sequence in context: A144038 A027842 A232043 * A027683 A196968 A000829

Adjacent sequences: A360503 A360504 A360505 * A360507 A360508 A360509

KEYWORD

nonn,base

AUTHOR

N. J. A. Sloane, Feb 17 2023

EXTENSIONS

More terms from Rémy Sigrist, Feb 18 2023

STATUS

approved