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A061472 First (leftmost) digit - second digit + third digit - fourth digit .... = 3.

%I A061472 #17 May 16 2020 17:11:27
%S A061472 3,30,41,52,63,74,85,96,102,113,124,135,146,157,168,179,201,212,223,
%T A061472 234,245,256,267,278,289,300,311,322,333,344,355,366,377,388,399,410,
%U A061472 421,432,443,454,465,476,487,498,520,531,542,553,564,575,586,597,630
%N A061472 First (leftmost) digit - second digit + third digit - fourth digit .... = 3.
%H A061472 Amiram Eldar, <a href="/A061472/b061472.txt">Table of n, a(n) for n = 1..10000</a>
%F A061472 A225693(n) = 3. - _Robert Israel_, Jun 12 2019
%e A061472 124 is in the sequence since 1 - 2 + 4 = 3.
%p A061472 A225693:= proc(n) local L,m,i;
%p A061472   L:= convert(n,base,10);
%p A061472   m:= nops(L);
%p A061472   add(L[i]*(-1)^(m-i),i=1..m);
%p A061472 end proc:
%p A061472 select(A225693=3, [$1..1000]); # _Robert Israel_, Jun 12 2019
%t A061472 aQ[n_] := Differences[Total @ Take[IntegerDigits[n], {#, -1, 2}] & /@ {2, 1}][[1]] == 3; Select[Range[1000], aQ] (* _Amiram Eldar_, Jun 12 2019 *)
%t A061472 Select[Range[1000],Total[Times@@@Partition[Riffle[IntegerDigits[#],{1,-1},{2,-1,2}],2]]==3&] (* _Harvey P. Dale_, May 16 2020 *)
%o A061472 (PARI) isok(n) = my(d=digits(n)); sum(k=1, #d, (-1)^(k+1)*d[k]) == 3; \\ _Michel Marcus_, Jun 12 2019
%Y A061472 Cf. A008593, A060978-A060980, A060982, A061470-A061479, A061870-A061882, A225693.
%K A061472 nonn,base,easy
%O A061472 1,1
%A A061472 _Amarnath Murthy_, May 05 2001
%E A061472 More terms from _Robert G. Wilson v_, May 10 2001 and from Larry Reeves (larryr(AT)acm.org), May 14 2001