A362680 a(n) is the number of decimal digits in A173426(n).

1, 3, 5, 7, 9, 11, 13, 15, 17, 20, 24, 28, 32, 36, 40, 44, 48, 52, 56, 60, 64, 68, 72, 76, 80, 84, 88, 92, 96, 100, 104, 108, 112, 116, 120, 124, 128, 132, 136, 140, 144, 148, 152, 156, 160, 164, 168, 172, 176, 180, 184, 188, 192, 196, 200, 204, 208, 212, 216, 220, 224, 228, 232

Offset

1,2

Links

Table of n, a(n) for n=1..63.

Formula

a(n) = A058183(n) + A058183(n-1), for n >= 2.

a(n) = A055642(A173426(n)).

a(n) = 2*A058183(n) - A055642(n).

Example

a(12)=28 since 1234567891011121110987654321 has 28 digits.

Prog

(PARI)
a(n)={my(t=logint(n, 10)+1); 2*n*t-2*(10^t-1)/9+t}
(Python)
def a(n): return ((n*(t:=len(str(n)))-(10**t-1)//9)<<1) + t
print([a(n) for n in range(1, 64)]) # Michael S. Branicky, May 02 2023

Crossrefs

Cf. A173426, A058183, A055642.

Sequence in context: A137507 A061808 A248608 * A309325 A368729 A192863

Adjacent sequences: A362677 A362678 A362679 * A362681 A362682 A362683

Keyword

nonn,base

Author

David Cleaver, Apr 29 2023

Status

approved