The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A297646

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A297646

Heptagonal numbers (A000566) in which parity of digits alternates.
(history; published version)

#10 by Harvey P. Dale at Thu Jul 14 14:59:43 EDT 2022

STATUS

editing

approved

#9 by Harvey P. Dale at Thu Jul 14 14:59:38 EDT 2022

LINKS

Harvey P. Dale, <a href="/A297646/b297646.txt">Table of n, a(n) for n = 1..500</a>

STATUS

approved

editing

#8 by Harvey P. Dale at Thu Jul 14 14:57:53 EDT 2022

STATUS

editing

approved

#7 by Harvey P. Dale at Thu Jul 14 14:57:50 EDT 2022

MATHEMATICA

Join[{1, 7}, Select[PolygonalNumber[7, Range[1000]], Union[Abs[Differences[ Boole[ OddQ[ IntegerDigits[ #]]]]]] =={1}&]] (* Harvey P. Dale, Jul 14 2022 *)

STATUS

approved

editing

#6 by Susanna Cuyler at Wed Jan 03 17:58:14 EST 2018

STATUS

proposed

approved

#5 by Felix Fröhlich at Wed Jan 03 02:51:55 EST 2018

STATUS

editing

proposed

#4 by Felix Fröhlich at Wed Jan 03 02:50:12 EST 2018

COMMENTS

Intersection of A000566 and A030141. - Felix Fröhlich, Jan 03 2018

CROSSREFS

Cf. A000566, A030141, A030152, A030160, A068882.

STATUS

proposed

editing

#3 by Colin Barker at Wed Jan 03 02:39:50 EST 2018

STATUS

editing

proposed

#2 by Colin Barker at Tue Jan 02 13:51:49 EST 2018

NAME

allocated for Colin BarkerHeptagonal numbers (A000566) in which parity of digits alternates.

DATA

1, 7, 18, 34, 81, 189, 616, 783, 874, 3010, 4141, 4347, 5452, 6943, 8323, 12145, 14707, 18361, 52345, 69472, 74563, 78943, 96727, 129618, 147258, 163456, 214183, 232105, 250747, 258727, 270109, 276723, 278389, 307476, 309232, 381616, 389470, 436183, 450925

OFFSET

1,2

EXAMPLE

6943 is in the sequence because 6, 9, 4 and 3 have even and odd parity alternately.

PROG

(PARI)

is_alt(n) = m=n; e=n%10; n\=10; while(n>0, f=n%10; if(e%2==f%2, return, e=f; n\=10)); return(m)

select(is_alt, vector(1000, n, (5*n^2-3*n)/2))

CROSSREFS

Cf. A297644, A297645, A297647.

Cf. A000566, A030152, A030160, A068882.

KEYWORD

allocated

nonn,base

AUTHOR

Colin Barker, Jan 02 2018

STATUS

approved

editing

#1 by Colin Barker at Tue Jan 02 12:48:25 EST 2018

NAME

allocated for Colin Barker

KEYWORD

allocated

STATUS

approved