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 A030465 Numbers k such that k concatenated with k+1 is a square. 20
 183, 328, 528, 715, 6099, 13224, 40495, 106755, 453288, 2066115, 2975208, 22145328, 28027683, 110213248, 110667555, 147928995, 178838403, 226123528, 275074575, 333052608, 378698224, 445332888, 446245635 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Also called Sastry numbers. - Lekraj Beedassy, Jul 18 2008 REFERENCES J.-M. De Koninck, Ces nombres qui nous fascinent, Entry 183, p. 56, Ellipses, Paris 2008. LINKS Giovanni Resta, Table of n, a(n) for n = 1..198 (terms < 10^20) MATHEMATICA Select[{#, FromDigits[Join[IntegerDigits[#], IntegerDigits[1 + #]]]} & /@ Flatten[Table[10*n + {0, 3, 4, 5, 8, 9}, {n, 10^5}]], IntegerQ[Sqrt[#[[2]]]] &] (* Hans Rudolf Widmer, Jun 30 2021 *) PROG (PARI) isok(k) = issquare(eval(concat(Str(k), Str(k+1)))); \\ Michel Marcus, Jun 30 2021 CROSSREFS Cf. A030466, A030467, A054214, A054215, A054216, A020339, A020340. Sequence in context: A264779 A133609 A305349 * A147270 A147124 A261110 Adjacent sequences: A030462 A030463 A030464 * A030466 A030467 A030468 KEYWORD nonn,base AUTHOR Patrick De Geest STATUS approved

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Last modified October 1 19:09 EDT 2023. Contains 365828 sequences. (Running on oeis4.)