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A321284 a(n) = 2*(2^(35*3^n) + 1). 0
68719476738, 81129638414606681695789005144066, 133499189745056880149688856635597007162669032647290798121690100488888732861290034376435130433538 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

Terms are a practical numbers.

a(3) has 285 digits.

LINKS

Table of n, a(n) for n=0..2.

Li-Yuan Wang and Zhi-Wei Sun, On practical numbers of some special forms, arXiv preprint arXiv:1809.01532 [math.NT], 2018.

FORMULA

a(n) = A005843(A000079(35*A000244(n)) + 1).

MAPLE

a := n -> 2*(2^(35*3^n)+1):

seq(a(n), n = 0 .. 5);

MATHEMATICA

a[n_]:=2*(2^(35*3^n)+1); Array[a, 5, 0]

PROG

(GAP) Flat(List([0..2], n->List([0..n], k->2*(2^(35*3^k)+1))));

(MAGMA) [2*(2^(35*3^n)+1): n in [0..5]];

(Maxima) a(n):=2*(2^(35*3^n)+1)$ makelist(a(n), n, 0, 5);

(PARI) a(n)=2*(2^(35*3^n)+1);

tabl(nn) = for(n=0, nn, print1(a(n), ", "));

tabl(5)

(Python) for n in range(5): print(2 * (2**(35 * 3**n) + 1), end=', ')

CROSSREFS

Cf. A005843, A000079, A000244, A005153 (practical number).

Subsequence of A321308.

Sequence in context: A017496 A017628 A139572 * A186095 A218397 A103617

Adjacent sequences:  A321281 A321282 A321283 * A321285 A321286 A321287

KEYWORD

nonn

AUTHOR

Stefano Spezia, Nov 02 2018

STATUS

approved

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Last modified August 7 06:24 EDT 2020. Contains 336274 sequences. (Running on oeis4.)