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A173427 Decimal value a(n) of the binary number b(n) obtained by starting from 1, sequentially concatenating all binary numbers up to n and then sequentially concatenating all binary numbers from n-1 down to 1. 23
1, 13, 221, 7069, 451997, 28931485, 1851651485, 237010810269, 60674754606493, 15532737233548701, 3976380732916495773, 1017953467644930815389, 260596087717395474544029, 66712598455657932715586973 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..14.

FORMULA

a(n) = binary_to_decimal(concatenate(1,10,11,..., binary(n-2), binary(n-1), binary(n), binary(n-1), binary(n-2),..., 11, 10, 1))

EXAMPLE

a(1)=binary_to_decimal(1)=1, a(2)=binary_to_decimal(1101)=13, a(3)=binary_to_decimal(11011101)=221, a(4)=binary_to_decimal(1101110011101)=7069 etc.

PROG

(PARI) a(n)=sum(i=1, #n=concat(vector(n*2-1, k, binary(min(k, n*2-k)))), n[i]<<(#n-i))

(PARI) A173427(n)={my(s=0, s1=0, t=0, b=0); for(k=1, n-1, s1+=k<<t+=b; k>>b&&b++; s=s<<b+k); t+=b; n>>b&&b++; (s<<b+n)<<t+s1} \\ M. F. Hasler, Aug 06 2015

CROSSREFS

Sequence in context: A086147 A015253 A051621 * A051180 A143832 A140841

Adjacent sequences:  A173424 A173425 A173426 * A173428 A173429 A173430

KEYWORD

base,nonn

AUTHOR

Umut Uludag, Feb 18 2010

STATUS

approved

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Last modified October 21 00:56 EDT 2017. Contains 293679 sequences.