A248131 -id:A248131 - cp's OEIS frontend

A102251 Begin with 1, multiply each digit by 2.

1, 2, 4, 8, 16, 2, 12, 4, 2, 4, 8, 4, 8, 16, 8, 16, 2, 12, 16, 2, 12, 4, 2, 4, 2, 12, 4, 2, 4, 8, 4, 8, 4, 2, 4, 8, 4, 8, 16, 8, 16, 8, 4, 8, 16, 8, 16, 2, 12, 16, 2, 12, 16, 8, 16, 2, 12, 16, 2, 12, 4, 2, 4, 2, 12, 4, 2, 4, 2, 12, 16, 2, 12, 4, 2, 4, 2, 12, 4, 2, 4, 8, 4, 8, 4, 2, 4, 8, 4, 8, 4, 2, 4

Offset: 0

Alexandre Wajnberg and Eric Angelini, Feb 18 2005

Same digits as A061581 without the memory of the groupings of the preceding digits. A bunch of sequences can be produced with this rule: a(n)=d*k beginning with 1,2,3... for k=2,3,...

			Read a(5)=16 which produces a(6)=2 because 1*2=2 and a(7)=12 because 6*2=12. Now read a(6)=2 which produces [a(7) is already written] a(8)=4 because 2*2=4.

Reinhard Zumkeller, Table of n, a(n) for n = 0..10000

Cf. A061581.

Cf. A248131.

a102251 n = a102251_list !! n
a102251_list = 1 : (map (* 2) $
               concatMap (map (read . return) . show) a102251_list)
-- Reinhard Zumkeller, Oct 02 2014

Flatten[ NestList[ Function[x, Flatten[ FromDigits /@ 2IntegerDigits[ x]]], 1, 15]] (* Robert G. Wilson v, Feb 21 2005 *)

d*2, beginning with 1

More terms from Robert G. Wilson v, Feb 21 2005

A248153 Start with a(0)=10, then a(n) = 7 times the n-th digit of the sequence.

Original entry on oeis.org

10, 7, 0, 49, 0, 28, 63, 0, 14, 56, 42, 21, 0, 7, 28, 35, 42, 28, 14, 14, 7, 0, 49, 14, 56, 21, 35, 28, 14, 14, 56, 7, 28, 7, 28, 49, 0, 28, 63, 7, 28, 35, 42, 14, 7, 21, 35, 14, 56, 7, 28, 7, 28, 35, 42, 49, 14, 56, 49, 14, 56, 28, 63, 0, 14, 56, 42, 21, 49, 14, 56, 21, 35

Offset: 0

M. F. Hasler, Oct 02 2014

This sequence was inspired by E. Angelini's post to the SeqFan list, cf. links.
a(0)=10 is the smallest possible choice to ensure that the digit 0 appears anywhere in the sequence. a(0)=1 would lead to the same sequence with the terms 0 removed.
By construction, all terms a(n), n>0, are divisible by 7, and a(n)/7 yields the sequence of digits of the (concatenated) terms of this sequence.
It is easy to show that the distance between two 0's is strictly increasing from one occurrence to the next one. Thus, the asymptotic density of terms and/or digits 0 is zero, and the sequence can never "enter a loop".

E. Angelini, Brute force density: triples and cubes, SeqFan list, Oct 01 2014

Cf. A248128, A248129, A248130, A248131.

a(n,s=10,m=7,d=[])={for(i=1,n,print1(s",");d=concat(d,if(s,digits(s)));s=m*d[1];d=vecextract(d,"^1"));s}

def aupton(nn):
    alst, astr = [10], "X10"
    for n in range(1, nn+1):
        alst.append(7 * int(astr[n]))
        astr += str(alst[-1])
    return alst
print(aupton(72)) # Michael S. Branicky, Oct 07 2021

cp's OEIS Frontend

A102251 Begin with 1, multiply each digit by 2.

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