

A231964


Lesser member of untouchable twin pairs, that is, such a(n) and a(n)+2 are untouchable (A005114).


6



246, 288, 290, 304, 322, 324, 406, 472, 516, 518, 624, 626, 668, 748, 766, 782, 802, 892, 894, 896, 934, 964, 1044, 1078, 1146, 1148, 1160, 1246, 1254, 1256, 1312, 1314, 1316, 1346, 1404, 1418, 1420, 1506, 1508, 1680, 1716, 1774, 1820, 1838, 1840, 1842, 1894
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OFFSET

1,1


COMMENTS

There are 2673 terms in this sequence when the 8153 terms of A005114, up to 60000, are taken into account.
Note that some numbers come up by pairs like (288,290) or (322,324), corresponding to untouchable triples. Others come up by groups of 3 like (892,894,896) or (1312,1314,1316), corresponding to untouchable quadruplets. For higher ntuplets, see A231965.


LINKS

Donovan Johnson, Table of n, a(n) for n = 1..10000
Eric Weisstein's World of Mathematics, Untouchable Number.
Wikipedia, Untouchable number


EXAMPLE

246 and 248 are untouchable, so 246 is in this sequence.


PROG

(PARI) lista() = {v = readvec("untouchable.log"); for (i=1, #v, vi = v[i]; if (vecsearch(v, vi+2, ), print1(vi, ", ")); ); } \\ Michel Marcus, Nov 16 2013


CROSSREFS

Cf. A005114, A231965.
Sequence in context: A023097 A098195 A214474 * A231965 A067916 A229577
Adjacent sequences: A231961 A231962 A231963 * A231965 A231966 A231967


KEYWORD

nonn


AUTHOR

Michel Marcus, Nov 16 2013


STATUS

approved



