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A292579 Inverse to A055643: Consider n as a number written in base 60, using 2 decimal digits for each base-60 digit (which we allow to be in the range 0 .. 99), and write n in base 10. 6
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

For the first 240000 terms, also the conversion of a digital clock display H:MM:SS to seconds, i.e., a(HMMSS) yields the number of seconds after midnight corresponding to that time, with leading zeros allowed: 0 <= H <= 24, 0 <= MM, SS <= 59.

Numbers where SS or MM etc. are > 59 are strictly spoken invalid in base 60. However, in order to "fill in the gaps" in a meaningful way, we simply do allow SS, MM, etc. to take values up to 99. (The ISO specification for writing time and date does actually allow SS to take values including 60 in order to account for leap seconds, as it allows H to be equal to 24 to denote midnight at the end of a day.) Therefore, a(60+k) = 60+k for k < 40, but a(100+k) = 60+k, a(200+k) = 120+k etc, for 0 <= k <= 99.

LINKS

Table of n, a(n) for n=0..109.

FORMULA

a(n) = n - [n/100]*40 - [n/10^4]*40*60 - [n\10^6]*40*60^2 - ..., where [.] denotes the floor function.

A292579 o A055643 = A001477 (the identity map on the set of nonnegative integers), i.e., for all n >= 0, A292579(A055643(n)) = n.

Also, A055643(A292579(n)) = n for all n in the range of A055643, which are the "valid base-60 numbers", i.e., excluding 60, ..., 99, 160, ..., 199 etc. The latter (60, ...) are "converted" by A055643 o A292579 to correct base-60 numbers, i.e., 60 -> 100, 99 = 60 + 39 -> 139, 9999 -> 14039 since 99*60 + 99 = 6039 = 1*60^2 + 40*60 + 39 = 14039[60].

EXAMPLE

Interpreted in base-60, HMMSS[60] = H*60^2 + MM*60 + SS. Thus, e.g., a(100) = 60, a(123456) = 12*3600 + 34*60 + 56 = 45296.

In contrast to (most) digital clocks, MM and SS may take values up to 99. For example, a(199) = 1*60 + 99 = 159.

PROG

(PARI) A292579(n)=fromdigits(digits(n, 100), 60)

CROSSREFS

Cf. A055643.

Sequence in context: A087156 A254109 A296086 * A262530 A291179 A290948

Adjacent sequences:  A292576 A292577 A292578 * A292580 A292581 A292582

KEYWORD

nonn,base

AUTHOR

M. F. Hasler, Jan 09 2018

STATUS

approved

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Last modified May 22 00:03 EDT 2018. Contains 304403 sequences. (Running on oeis4.)