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A124241 Terms of A068563 that are not terms of A124240. 3
136, 408, 620, 680, 820, 1224, 1240, 1314, 2040, 2312, 2460, 2480, 2628, 2856, 3100, 3400, 3672, 3924, 3942, 4100, 4112, 4656, 4960, 5304, 5334, 5784, 6120, 6200, 6820, 6936, 7380, 7480, 7848, 7884, 8224, 8568, 9020, 9060, 9198, 9492, 9920, 10200, 10668, 11016, 11560, 11568, 11826, 12300, 12336, 12400, 13140, 13640 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

A068563 contains A124240 as a subsequence. This sequence gives their set difference.

Note that a(2) = 3*a(1) and a(4) = 5*a(1). a(6) = 1224 = 9*a(1), a(7) = 1240 = 2*a(3), a(8) = 1314, a(9) = 2040 = 15*a(1), a(10) = 2312 = 17*a(1), a(11) = 2460 = 3*a(5), a(12)= 2480 = 4*a(3), a(13) = 2856 = 21*a(1). Numbers k such that there exists a(n) = k*a(1) are k = {1, 3, 5, 9, 15, 17, 21, ...}.

Many but not all terms belong to A124276.

LINKS

Table of n, a(n) for n=1..52.

PROG

(PARI) for(n=1, 10^5, m=n\2^valuation(n, 2); if( Mod(n, znorder(Mod(2, m))), next); p=factor(n)[, 1]; g=1; for(i=1, #p, if( Mod(n, p[i]-1), g=0; break) ); if(g, next); print1(n, ", ") ) /* Alekseyev */

CROSSREFS

Cf. A124240, A124239, A068563, A124276, A064896.

Sequence in context: A247439 A183635 A116223 * A235198 A235191 A076331

Adjacent sequences:  A124238 A124239 A124240 * A124242 A124243 A124244

KEYWORD

nonn

AUTHOR

Alexander Adamchuk, Oct 22 2006, Oct 27 2006

EXTENSIONS

a(13) corrected and terms a(14) onward provided by Max Alekseyev, Aug 25 2013

STATUS

approved

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Last modified October 22 01:46 EDT 2020. Contains 337948 sequences. (Running on oeis4.)